java tuning

Garbage collection is the VM process of de-allocating unused Java objects in the Java heap. The Java heap is where the objects of a Java program live. It is a repository for live objects dead objects and free memory. When an object can no longer be reached from any pointer in the running program the object is garbage. The JVM heap size determines how often and how long the VM spends collecting garbage. An acceptable rate for garbage collection is application-specific and should be adjusted after analyzing the actual time and frequency of garbage collections. If you set a large heap size full garbage collection is slower but it occurs less frequently. If you set your heap size in accordance with your memory needs full garbage collection is faster but occurs more frequently. The goal of tuning your heap size is to minimize the time that you spend doing garbage collection while maximizing the number of clients that you can handle at a given time. To ensure maximum performance during benchmarking you might set high heap size values to ensure that garbage collection does not occur during the entire run of the benchmark. You might see the following java error if you are running out of heap space:

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What are difference between post database commit and post-form commit?Post-form act fires once during the post and commit transactions process after the database act occurs. The post-form-commit trigger fires after inserts updates and deletes undergo been posted to the database but before the transactions have been finalized in the issuing the command. The post-database-commit initiate fires after oracle forms issues the act to finalized transactions. What is an administrative (privileged) user? (for DBA )Oracle DBAs and operators typically use administrative accounts to manage the database and database dilate. An administrative account is a user that is granted SYSOPER or SYSDBA privileges. SYSDBA and SYSOPER accept find to a database dilate even if it is not running. Control of these privileges is managed outside of the database via password files and special operating system groups. This password register is created with the orapwd utility. How does one connect to an administrative user? (for DBA )If an administrative user belongs to the "dba" group on Unix or the "ORA_DBA" (ORA_sid_DBA) assort on NT he/she can connect desire this:connect / as sysdbaNo password is required. This is equivalent to the desupported "connect internal" method. A password is required for "non-secure" administrative access. These passwords are stored in password files. Remote connections via Net8 are classified as non-secure. Look at this example:connect sys/password as sysdba How does one act a password file? (for DBA )The Oracle Password File ($ORACLE_domiciliate/dbs/orapw or orapwSID) stores passwords for users with administrative privileges. One needs to create a password files before remote administrators (like OEM) will be allowed to cerebrate. go this procedure to act a new password register:. Log in as the Oracle software owner. Runcommand: orapwd file=$ORACLE_HOME/dbs/orapw$ORACLE_SID password=mypasswd. Shutdown the database (SQLPLUS> SHUTDOWN IMMEDIATE). Edit the INIT. ORA file and ensure REMOTE_LOGIN_PASSWORDFILE=exclusive is set.. Startup the database (SQLPLUS> STARTUP)NOTE: The orapwd utility presents a security assay in that it receives a password from the dominate line. This password is visible in the affect delay of many systems. Administrators needs to be aware of this! Why are OPS$ accounts a security risk in a client/server environment? (for DBA )If you accept populate to log in with OPS$ accounts from Windows Workstations you cannot be sure who they really are. With terminals you can believe on operating system passwords with Windows you cannot. If you set REMOTE_OS_AUTHENT=TRUE in your init ora register. Oracle assumes that the remote OS has authenticated the user. If REMOTE_OS_AUTHENT is set to FALSE (recommended) remote users ordain be unable to connect without a password. IDENTIFIED EXTERNALLY will only be in effect from the local entertain. Also if you are using "OPS$" as your prefix you ordain be able to log on locally with or without a password regardless of whether you have identified your ID with a password or defined it to be IDENTIFIED EXTERNALLY. What are modal windows?Modal windows are usually used as dialogs and have restricted functionality compared to modelless windows. On some platforms for example operators cannot resize scroll or iconify a modal window. What are the different default triggers created when Master Deletes Property is set to Non-isolated?know Deletes Property Resulting Triggers----------------------------------------------------Non-Isolated(the default) On-Check-Delete-MasterOn-Clear-DetailsOn-Populate-Details What are the different default triggers created when Master Deletes Property is set to isolated?Master Deletes Property Resulting Triggers---------------------------------------------------Isolated On-Clear-DetailsOn-Populate-Details What are the different default triggers created when Master Deletes Property is set to come down?Master Deletes Property Resulting Triggers---------------------------------------------------Cascading On-Clear-DetailsOn-Populate-DetailsPre-delete What is the advantage of the library?Libraries give a convenient means of storing client-side schedule units and sharing them among multiple applications. Once you act a library you can attach it to any other form menu or library modules. When you can call library program units from triggers menu items commands and user named routine you write in the modules to which you undergo attach the library. When a library attaches another library schedule units in the first library can reference schedule units in the attached library. Library support dynamic loading-that is library program units are loaded into an application only when needed. This can significantly decrease the run-time memory requirements of applications. What is lexical compose? How can it be created?Lexical compose is displace_holder for text that can be embedded in a sql statements. A lexical reference can be created using & before the column or parameter label. What are the built-ins used for processing rows?Get_assort_row_count(function)Get_group_selection_ascertain(answer)Get_group_selection(function)Reset_assort_selection(procedure)Set_assort_selection(procedure)Unset_assort_selection(procedure) What are built-ins used for Processing rows?GET_GROUP_ROW_COUNT(answer)GET_assort_SELECTION_COUNT(function)GET_assort_SELECTION(answer)RESET_assort_SELECTION(procedure)SET_GROUP_SELECTION(procedure)UNSET_GROUP_SELECTION(procedure) What are different types of modules available in oracle create?Form module - a collection of objects and label routines Menu modules - a collection of menus and menu item commands that together make up an application menu library module - a collection of user named procedures functions and packages that can be called from other modules in the application What is WHEN-Database-record trigger?Fires when oracle forms first marks a record as an attach or an update. The trigger fires as soon as oracle forms determines through validation that the preserve should be processed by the next post or act as an insert or update c generally occurs only when the operators modifies the first item in the record and after the operator attempts to journey out of the item. What is a difference between pre-select and pre-query?Fires during the kill query and count ask processing after oracle forms constructs the select statement to be issued but before the statement is actually issued. The pre-query initiate fires just before oracle forms issues the select statement to the database after the operator as be the example records by entering the query criteria in register query mode. Pre-query trigger fires before pre-select trigger. What third celebrate tools can be used with Oracle EBU/ RMAN? (for DBA)The following Media Management Software Vendors have integrated their media management software packages with Oracle Recovery Manager and Oracle7 Enterprise Backup Utility. The Media Management Vendors will provide first line technical give for the integrated backup/recover solutions. Veritas NetBackupEMC Data Manager (EDM)HP OMNIBack IIIBM's Tivoli Storage Manager - formerly ADSMLegato NetworkerManageIT Backup and RecoverySterling Software's SAMS:Alexandria - formerly from SpectralogicSun Solstice Backup Why and when should one tune? (for DBA)One of the biggest responsibilities of a DBA is to ensure that the Oracle database is tuned properly. The Oracle RDBMS is highly tunable and allows the database to be monitored and adjusted to change magnitude its performance. One should do performance tuning for the following reasons:The go of computing might be wasting valuable human measure (users waiting for response); alter your system to keep-up with the speed business is conducted; and Optimize hardware usage to save money (companies are spending millions on hardware). Although this FAQ is not overly concerned with hardware issues one needs to remember than you cannot tune a Buick into a Ferrari. What is the use of place holder column? What are the various sub events a mouse manifold move event involves?A placeholder column is used to hold calculated values at a specified place rather than allowing is to appear in the actual row where it has to appear. What database aspects should be monitored? (for DBA)One should apply a monitoring system to constantly monitor the following aspects of a database. Writing custom scripts implementing Oracle's Enterprise Manager or buying a third-party monitoring product can achieve this. If an affright is triggered the system should automatically notify the DBA (telecommunicate page etc.) to take appropriate challenge. Infrastructure availability:. Is the database up and responding to requests. Are the listeners up and responding to requests. Are the Oracle Names and LDAP Servers up and responding to requests. Are the Web Listeners up and responding to requestsThings that can create service outages:. Is the collect log destination filling up?. Objects getting close to their max extents. User and process limits reachedThings that can create bad performance:See question "What tuning indicators can one use?". Where should the tuning effort be directed? (for DBA)believe the following areas for tuning. The request in which steps are listed needs to be maintained to prevent tuning side effects. For example it is no good increasing the buffer lay aside if you can reduce I/O by rewriting a SQL statement. Database Design (if it's not too late):Poor system performance usually results from a poor database create by mental act. One should generally normalize to the 3NF. Selective denormalization can provide valuable performance improvements. When designing always keep the "data find path" in mind. Also look at proper data partitioning data replication aggregation tables for decision support systems etc. Application Tuning:undergo showed that approximately 80% of all Oracle system performance problems are resolved by coding optimal SQL. Also believe proper scheduling of group tasks after peak working hours. Memory Tuning:Properly coat your database buffers (shared pool modify lay aside log buffer etc) by looking at your buffer hit ratios. Pin large objects into memory to prevent frequent reloads. plough I/O Tuning:Database files needs to be properly sized and placed to provide maximum disk subsystem throughput. Also look for back up plough sorts full table scans missing indexes row chaining data fragmentation etcEliminate Database Contention:chew over database locks latches and act events carefully and eliminate where possible. Tune the Operating System:observe and adjust operating system CPU. I/O and memory utilization. For more information read the related Oracle FAQ dealing with your specific operating system. What are the various sub events a mouse double click event involves? What are the various sub events a mouse double click event involves?Double clicking the mouse consists of the walk drink mouse up mouse move walk down & mouse up events. What is relation between the window and beg views?Canvas views are the back ground objects on which you place the interface items (Text items) analyse boxes communicate groups etc.,) and boilerplate objects (boxes lines images etc.,) that operators interact with us they run your form. Each beg views displayed in a window. Does one be to drop/ truncate objects before importing? (for DBA)Before one import rows into already populated tables one needs to exchange or displace these tables to get rid of the old data. If not the new data will be appended to the existing tables. One must always DROP existing Sequences before re-importing. If the sequences are not dropped they will create numbers inconsistent with the rest of the database. Note: It is also advisable to displace indexes before importing to speed up the merchandise process. Indexes can easily be recreated after the data was successfully imported. Can one merchandise/merchandise between different versions of Oracle? (for DBA)Different versions of the import utility is upwards compatible. This means that one can act an export file created from an old export version and merchandise it using a later version of the merchandise utility. This is quite an effective way of upgrading a database from one release of Oracle to the next. Oracle also ships some previous catexpX sql scripts that can be executed as user SYS enabling older imp/exp versions to work (for backwards compatibility). For example one can run $ORACLE_domiciliate/rdbms/admin/catexp7 sql on an Oracle 8 database to accept the Oracle 7.3 exp/imp utilities to run against an Oracle 8 database. Can one export to multiple files?/ Can one defeat the Unix 2 Gig check? (for DBA)From Oracle8i the merchandise utility supports multiple create files. This feature enables large exports to be divided into files whose sizes will not exceed any operating system limits (FILESIZE= parameter). When importing from multi-file export you must provide the same filenames in the same grade in the FILE= parameter. Look at this example:exp SCOTT/TIGER FILE=D:\F1 dmp,E:\F2 dmp FILESIZE=10m LOG=scott logUse the following technique if you use an Oracle version prior to 8i:act a compressed export on the fly. Depending on the write of data you probably can export up to 10 gigabytes to a single file. This example uses gzip. It offers the best compression I know of but you can also alter it with zip compress or whatever.# create a named pipemknod exp pipe p# construe the pipe - create to zip file in the backgroundgzip What is bind reference and how can it be created?attach reference are used to regenerate the hit value in sql pl/sql statements a bind compose can be created using a (:) before a column or a parameter label. How can one alter merchandise/ merchandise performance? (for DBA)EXPORT:. Set the BUFFER parameter to a high determine (e g. 2M). Set the RECORDLENGTH parameter to a high determine (e g. 64K). Stop unnecessary applications to free-up resources for your job.. If you run multiple merchandise sessions ensure they write to different physical disks.. DO NOT merchandise to an NFS mounted filesystem. It ordain take forever. merchandise:. Create an indexfile so that you can create indexes AFTER you have imported data. Do this by setting INDEXFILE to a filename and then import. No data ordain be imported but a file containing index definitions ordain be created. You must edit this file afterwards and supply the passwords for the schemas on all cerebrate statements.. Place the file to be imported on a displace physical plough from the oracle data files. Increase DB_lay aside_SIZE (DB_block_BUFFERS prior to 9i) considerably in the init$SID ora file. Set the LOG_modify to a big value and start oracle.. Stop create log archiving if it is running (ALTER DATABASE NOARCHIVELOG;). Create a BIG tablespace with a BIG rollback segment inside. Set all other rollback segments offline (object the SYSTEM rollback segment of course). The rollback divide must be as big as your biggest table (I evaluate?). Use COMMIT=N in the import parameter register if you can afford it. Use ANALYZE=N in the import parameter register to forbid measure consuming ANALYZE statements. Remember to run the indexfile previously created What are the common Import/ merchandise problems? (for DBA )ORA-00001: Unique constraint (...) violated - You are importing duplicate rows. Use IGNORE=NO to drop tables that already exist (imp ordain furnish an error if the object is re-created). ORA-01555: Snapshot too old - Ask your users to forbid working while you are exporting or use parameter CONSISTENT=NOORA-01562: Failed to increase rollback divide - act bigger rollback segments or set parameter COMMIT=Y while importingIMP-00015: Statement failed.. object already exists... - Use the IGNORE=Y import parameter to do by these errors but be careful as you might end up with duplicate rows.

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What are difference between affix database commit and post-form act?Post-form commit fires once during the post and commit transactions affect after the database act occurs. The post-form-commit initiate fires after inserts updates and deletes undergo been posted to the database but before the transactions undergo been finalized in the issuing the dominate. The post-database-commit trigger fires after oracle forms issues the act to finalized transactions. What is an administrative (privileged) user? (for DBA )Oracle DBAs and operators typically use administrative accounts to bring home the bacon the database and database instance. An administrative account is a user that is granted SYSOPER or SYSDBA privileges. SYSDBA and SYSOPER accept access to a database instance change surface if it is not running. Control of these privileges is managed outside of the database via password files and special operating system groups. This password register is created with the orapwd utility. How does one connect to an administrative user? (for DBA )If an administrative user belongs to the "dba" group on Unix or the "ORA_DBA" (ORA_sid_DBA) group on NT he/she can connect like this:connect / as sysdbaNo password is required. This is equivalent to the desupported "connect internal" method. A password is required for "non-secure" administrative access. These passwords are stored in password files. Remote connections via Net8 are classified as non-secure. be at this example:connect sys/password as sysdba How does one act a password file? (for DBA )The Oracle Password register ($ORACLE_domiciliate/dbs/orapw or orapwSID) stores passwords for users with administrative privileges. One needs to create a password files before remote administrators (like OEM) ordain be allowed to cerebrate. Follow this procedure to act a new password register:. Log in as the Oracle software owner. Runcommand: orapwd file=$ORACLE_HOME/dbs/orapw$ORACLE_SID password=mypasswd. Shutdown the database (SQLPLUS> SHUTDOWN IMMEDIATE). Edit the INIT. ORA file and ensure REMOTE_LOGIN_PASSWORDFILE=exclusive is set.. Startup the database (SQLPLUS> STARTUP)say: The orapwd utility presents a security assay in that it receives a password from the dominate lie. This password is visible in the process delay of many systems. Administrators needs to be aware of this! Why are OPS$ accounts a security risk in a client/server environment? (for DBA )If you accept people to log in with OPS$ accounts from Windows Workstations you cannot be sure who they really are. With terminals you can rely on operating system passwords with Windows you cannot. If you set REMOTE_OS_AUTHENT=TRUE in your init ora file. Oracle assumes that the remote OS has authenticated the user. If REMOTE_OS_AUTHENT is set to FALSE (recommended) remote users will be unable to cerebrate without a password. IDENTIFIED EXTERNALLY will only be in cause from the local host. Also if you are using "OPS$" as your affix you will be able to log on locally with or without a password regardless of whether you have identified your ID with a password or defined it to be IDENTIFIED EXTERNALLY. What are modal windows?Modal windows are usually used as dialogs and have restricted functionality compared to modelless windows. On some platforms for example operators cannot resize scroll or iconify a modal window. What are the different fail triggers created when Master Deletes Property is set to Non-isolated?know Deletes Property Resulting Triggers----------------------------------------------------Non-Isolated(the fail) On-Check-Delete-MasterOn-Clear-DetailsOn-Populate-Details What are the different fail triggers created when Master Deletes Property is set to isolated?Master Deletes Property Resulting Triggers---------------------------------------------------Isolated On-Clear-DetailsOn-Populate-Details What are the different default triggers created when Master Deletes Property is set to come down?know Deletes Property Resulting Triggers---------------------------------------------------Cascading On-Clear-DetailsOn-Populate-DetailsPre-delete What is the advantage of the library?Libraries provide a convenient means of storing client-side schedule units and sharing them among multiple applications. Once you create a library you can connect it to any other create menu or library modules. When you can call library schedule units from triggers menu items commands and user named routine you write in the modules to which you have attach the library. When a library attaches another library program units in the first library can reference schedule units in the attached library. Library give dynamic loading-that is library program units are loaded into an application only when needed. This can significantly decrease the run-time memory requirements of applications. What is lexical compose? How can it be created?Lexical compose is place_holder for text that can be embedded in a sql statements. A lexical reference can be created using & before the column or parameter label. What are the built-ins used for processing rows?Get_group_row_ascertain(function)Get_group_selection_ascertain(function)Get_group_selection(function)Reset_group_selection(procedure)Set_assort_selection(procedure)Unset_assort_selection(procedure) What are built-ins used for Processing rows?GET_GROUP_ROW_ascertain(function)GET_assort_SELECTION_ascertain(function)GET_assort_SELECTION(answer)RESET_assort_SELECTION(procedure)SET_GROUP_SELECTION(procedure)UNSET_assort_SELECTION(procedure) What are different types of modules available in oracle form?Form module - a collection of objects and code routines Menu modules - a collection of menus and menu item commands that together alter up an application menu library module - a collection of user named procedures functions and packages that can be called from other modules in the application What is WHEN-Database-record trigger?Fires when oracle forms first marks a preserve as an attach or an update. The trigger fires as soon as oracle forms determines through validation that the record should be processed by the next affix or commit as an attach or modify c generally occurs only when the operators modifies the first item in the record and after the operator attempts to navigate out of the item. What is a difference between pre-select and pre-query?Fires during the kill ask and count query processing after oracle forms constructs the select statement to be issued but before the statement is actually issued. The pre-query trigger fires just before oracle forms issues the select statement to the database after the operator as be the example records by entering the query criteria in register query mode. Pre-query trigger fires before pre-select trigger. What third party tools can be used with Oracle EBU/ RMAN? (for DBA)The following Media Management Software Vendors undergo integrated their media management software packages with Oracle Recovery Manager and Oracle7 Enterprise Backup Utility. The Media Management Vendors will provide first line technical support for the integrated backup/recover solutions. Veritas NetBackupEMC Data Manager (EDM)HP OMNIBack IIIBM's Tivoli Storage Manager - formerly ADSMLegato NetworkerManageIT Backup and RecoverySterling Software's SAMS:Alexandria - formerly from SpectralogicSun Solstice Backup Why and when should one adjust? (for DBA)One of the biggest responsibilities of a DBA is to ensure that the Oracle database is tuned properly. The Oracle RDBMS is highly tunable and allows the database to be monitored and adjusted to increase its performance. One should do performance tuning for the following reasons:The go of computing might be wasting valuable human time (users waiting for response); alter your system to keep-up with the speed business is conducted; and Optimize hardware usage to deliver money (companies are spending millions on hardware). Although this FAQ is not overly concerned with hardware issues one needs to bequeath than you cannot tune a Buick into a Ferrari. What is the use of place holder column? What are the various sub events a mouse manifold click event involves?A placeholder column is used to hold calculated values at a specified place rather than allowing is to be in the actual row where it has to appear. What database aspects should be monitored? (for DBA)One should apply a monitoring system to constantly observe the following aspects of a database. Writing custom scripts implementing Oracle's Enterprise Manager or buying a third-party monitoring product can achieve this. If an alarm is triggered the system should automatically notify the DBA (telecommunicate summon etc.) to take appropriate action. Infrastructure availability:. Is the database up and responding to requests. Are the listeners up and responding to requests. Are the Oracle Names and LDAP Servers up and responding to requests. Are the Web Listeners up and responding to requestsThings that can cause function outages:. Is the collect log destination filling up?. Objects getting change state to their max extents. User and process limits reachedThings that can create bad performance:See challenge "What tuning indicators can one use?". Where should the tuning effort be directed? (for DBA)believe the following areas for tuning. The order in which steps are listed needs to be maintained to prevent tuning side effects. For example it is no good increasing the modify cache if you can reduce I/O by rewriting a SQL statement. Database create by mental act (if it's not too late):Poor system performance usually results from a poor database design. One should generally change to the 3NF. Selective denormalization can provide valuable performance improvements. When designing always keep the "data access path" in object. Also look at proper data partitioning data replication aggregation tables for decision give systems etc. Application Tuning:undergo showed that approximately 80% of all Oracle system performance problems are resolved by coding optimal SQL. Also consider proper scheduling of group tasks after peak working hours. Memory Tuning:Properly coat your database buffers (shared share modify lay aside log buffer etc) by looking at your buffer hit ratios. Pin large objects into memory to prevent frequent reloads. plough I/O Tuning:Database files needs to be properly sized and placed to provide maximum disk subsystem throughput. Also look for frequent plough sorts beat table scans missing indexes row chaining data fragmentation etcEliminate Database Contention:Study database locks latches and act events carefully and destroy where possible. Tune the Operating System:Monitor and tune operating system CPU. I/O and memory utilization. For more information read the related Oracle FAQ dealing with your specific operating system. What are the various sub events a mouse double move event involves? What are the various sub events a mouse manifold move event involves?Double clicking the mouse consists of the mouse down walk up mouse click walk down & mouse up events. What is relation between the window and beg views?beg views are the back fasten objects on which you place the interface items (Text items) check boxes communicate groups etc.,) and boilerplate objects (boxes lines images etc.,) that operators act with us they run your form. Each canvas views displayed in a window. Does one be to drop/ truncate objects before importing? (for DBA)Before one import rows into already populated tables one needs to truncate or drop these tables to get rid of the old data. If not the new data will be appended to the existing tables. One must always DROP existing Sequences before re-importing. If the sequences are not dropped they will generate numbers inconsistent with the be of the database. Note: It is also advisable to drop indexes before importing to speed up the merchandise affect. Indexes can easily be recreated after the data was successfully imported. Can one import/export between different versions of Oracle? (for DBA)Different versions of the import utility is upwards compatible. This means that one can take an merchandise file created from an old merchandise version and merchandise it using a later version of the import utility. This is quite an effective way of upgrading a database from one release of Oracle to the next. Oracle also ships some previous catexpX sql scripts that can be executed as user SYS enabling older imp/exp versions to bring home the bacon (for backwards compatibility). For example one can run $ORACLE_HOME/rdbms/admin/catexp7 sql on an Oracle 8 database to allow the Oracle 7.3 exp/imp utilities to run against an Oracle 8 database. Can one merchandise to multiple files?/ Can one defeat the Unix 2 Gig limit? (for DBA)From Oracle8i the export utility supports multiple create files. This feature enables large exports to be divided into files whose sizes will not exceed any operating system limits (FILESIZE= parameter). When importing from multi-file export you must give the same filenames in the same grade in the FILE= parameter. Look at this example:exp SCOTT/TIGER register=D:\F1 dmp,E:\F2 dmp FILESIZE=10m LOG=scott logUse the following technique if you use an Oracle version prior to 8i:act a compressed merchandise on the fly. Depending on the type of data you probably can merchandise up to 10 gigabytes to a hit register. This example uses gzip. It offers the best compression I know of but you can also alter it with zip force or whatever.# create a named pipemknod exp pipe p# read the pipe - create to zip register in the backgroundgzip What is bind reference and how can it be created?Bind compose are used to regenerate the hit value in sql pl/sql statements a attach reference can be created using a (:) before a column or a parameter name. How can one improve Import/ Export performance? (for DBA)merchandise:. Set the BUFFER parameter to a high value (e g. 2M). Set the RECORDLENGTH parameter to a high determine (e g. 64K). Stop unnecessary applications to free-up resources for your job.. If you run multiple merchandise sessions ensure they write to different physical disks.. DO NOT merchandise to an NFS mounted filesystem. It ordain act forever. IMPORT:. act an indexfile so that you can create indexes AFTER you have imported data. Do this by setting INDEXFILE to a filename and then merchandise. No data will be imported but a file containing index definitions ordain be created. You must edit this register afterwards and supply the passwords for the schemas on all CONNECT statements.. Place the file to be imported on a separate physical plough from the oracle data files. Increase DB_lay aside_SIZE (DB_block_BUFFERS prior to 9i) considerably in the init$SID ora file. Set the LOG_BUFFER to a big value and restart oracle.. forbid redo log archiving if it is running (alter DATABASE NOARCHIVELOG;). act a BIG tablespace with a BIG rollback segment inside. Set all other rollback segments offline (object the SYSTEM rollback segment of cover). The rollback segment must be as big as your biggest table (I think?). Use act=N in the import parameter file if you can afford it. Use care for=N in the import parameter register to avoid time consuming care for statements. Remember to run the indexfile previously created What are the common Import/ Export problems? (for DBA )ORA-00001: Unique constraint (...) violated - You are importing reproduce rows. Use IGNORE=NO to skip tables that already exist (imp ordain give an error if the object is re-created). ORA-01555: Snapshot too old - Ask your users to STOP working while you are exporting or use parameter CONSISTENT=NOORA-01562: Failed to extend rollback segment - Create bigger rollback segments or set parameter COMMIT=Y while importingIMP-00015: Statement failed.. object already exists... - Use the IGNORE=Y import parameter to ignore these errors but be careful as you might end up with duplicate rows.

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What are difference between post database commit and post-form act?Post-form commit fires once during the post and act transactions process after the database act occurs. The post-form-commit trigger fires after inserts updates and deletes undergo been posted to the database but before the transactions undergo been finalized in the issuing the dominate. The post-database-commit trigger fires after oracle forms issues the commit to finalized transactions. What is an administrative (privileged) user? (for DBA )Oracle DBAs and operators typically use administrative accounts to bring home the bacon the database and database instance. An administrative account is a user that is granted SYSOPER or SYSDBA privileges. SYSDBA and SYSOPER allow access to a database instance even if it is not running. hold back of these privileges is managed outside of the database via password files and special operating system groups. This password file is created with the orapwd utility. How does one connect to an administrative user? (for DBA )If an administrative user belongs to the "dba" group on Unix or the "ORA_DBA" (ORA_sid_DBA) assort on NT he/she can cerebrate desire this:connect / as sysdbaNo password is required. This is equivalent to the desupported "connect internal" method. A password is required for "non-secure" administrative access. These passwords are stored in password files. Remote connections via Net8 are classified as non-secure. be at this example:cerebrate sys/password as sysdba How does one act a password file? (for DBA )The Oracle Password File ($ORACLE_HOME/dbs/orapw or orapwSID) stores passwords for users with administrative privileges. One needs to act a password files before remote administrators (desire OEM) ordain be allowed to cerebrate. go this procedure to act a new password file:. Log in as the Oracle software owner. Runcommand: orapwd register=$ORACLE_HOME/dbs/orapw$ORACLE_SID password=mypasswd. Shutdown the database (SQLPLUS> SHUTDOWN IMMEDIATE). Edit the INIT. ORA register and ensure REMOTE_LOGIN_PASSWORDFILE=exclusive is set.. Startup the database (SQLPLUS> STARTUP)NOTE: The orapwd utility presents a security assay in that it receives a password from the command lie. This password is visible in the process table of many systems. Administrators needs to be aware of this! Why are OPS$ accounts a security risk in a client/server environment? (for DBA )If you allow people to log in with OPS$ accounts from Windows Workstations you cannot be sure who they really are. With terminals you can rely on operating system passwords with Windows you cannot. If you set REMOTE_OS_AUTHENT=adjust in your init ora register. Oracle assumes that the remote OS has authenticated the user. If REMOTE_OS_AUTHENT is set to FALSE (recommended) remote users ordain be unable to connect without a password. IDENTIFIED EXTERNALLY will only be in effect from the local entertain. Also if you are using "OPS$" as your prefix you ordain be able to log on locally with or without a password regardless of whether you undergo identified your ID with a password or defined it to be IDENTIFIED EXTERNALLY. What are modal windows?Modal windows are usually used as dialogs and have restricted functionality compared to modelless windows. On some platforms for example operators cannot resize move or iconify a modal window. What are the different default triggers created when know Deletes Property is set to Non-isolated?Master Deletes Property Resulting Triggers----------------------------------------------------Non-Isolated(the fail) On-Check-Delete-MasterOn-Clear-DetailsOn-Populate-Details What are the different default triggers created when Master Deletes Property is set to isolated?Master Deletes Property Resulting Triggers---------------------------------------------------Isolated On-Clear-DetailsOn-Populate-Details What are the different fail triggers created when know Deletes Property is set to Cascade?Master Deletes Property Resulting Triggers---------------------------------------------------Cascading On-Clear-DetailsOn-Populate-DetailsPre-delete What is the favor of the library?Libraries provide a convenient means of storing client-side program units and sharing them among multiple applications. Once you create a library you can attach it to any other create menu or library modules. When you can call library program units from triggers menu items commands and user named routine you write in the modules to which you undergo connect the library. When a library attaches another library program units in the first library can compose program units in the attached library. Library give dynamic loading-that is library program units are loaded into an application only when needed. This can significantly reduce the run-time memory requirements of applications. What is lexical reference? How can it be created?Lexical compose is place_holder for text that can be embedded in a sql statements. A lexical reference can be created using & before the column or parameter name. What are the built-ins used for processing rows?Get_assort_row_ascertain(answer)Get_assort_selection_ascertain(function)Get_assort_selection(answer)define_assort_selection(procedure)Set_group_selection(procedure)Unset_assort_selection(procedure) What are built-ins used for Processing rows?GET_GROUP_ROW_ascertain(answer)GET_GROUP_SELECTION_ascertain(answer)GET_GROUP_SELECTION(answer)define_GROUP_SELECTION(procedure)SET_GROUP_SELECTION(procedure)UNSET_assort_SELECTION(procedure) What are different types of modules available in oracle form?Form module - a collection of objects and code routines Menu modules - a collection of menus and menu item commands that together make up an application menu library module - a collection of user named procedures functions and packages that can be called from other modules in the application What is WHEN-Database-record trigger?Fires when oracle forms first marks a record as an insert or an update. The initiate fires as soon as oracle forms determines through validation that the record should be processed by the next post or commit as an insert or modify c generally occurs only when the operators modifies the first item in the preserve and after the operator attempts to journey out of the item. What is a difference between pre-select and pre-query?Fires during the execute query and count ask processing after oracle forms constructs the select statement to be issued but before the statement is actually issued. The pre-query trigger fires just before oracle forms issues the decide statement to the database after the operator as be the example records by entering the ask criteria in enter query mode. Pre-query initiate fires before pre-select trigger. What third party tools can be used with Oracle EBU/ RMAN? (for DBA)The following Media Management Software Vendors undergo integrated their media management software packages with Oracle Recovery Manager and Oracle7 Enterprise Backup Utility. The Media Management Vendors ordain give first line technical support for the integrated backup/recover solutions. Veritas NetBackupEMC Data Manager (EDM)HP OMNIBack IIIBM's Tivoli Storage Manager - formerly ADSMLegato NetworkerManageIT Backup and RecoverySterling Software's SAMS:Alexandria - formerly from SpectralogicSun Solstice Backup Why and when should one adjust? (for DBA)One of the biggest responsibilities of a DBA is to ensure that the Oracle database is tuned properly. The Oracle RDBMS is highly tunable and allows the database to be monitored and adjusted to increase its performance. One should do performance tuning for the following reasons:The speed of computing might be wasting valuable human time (users waiting for response); Enable your system to keep-up with the speed business is conducted; and Optimize hardware usage to save money (companies are spending millions on hardware). Although this FAQ is not overly concerned with hardware issues one needs to remember than you cannot tune a Buick into a Ferrari. What is the use of place holder column? What are the various sub events a mouse manifold click event involves?A placeholder column is used to direct calculated values at a specified place rather than allowing is to appear in the actual row where it has to appear. What database aspects should be monitored? (for DBA)One should apply a monitoring system to constantly monitor the following aspects of a database. Writing custom scripts implementing Oracle's Enterprise Manager or buying a third-party monitoring product can bring home the bacon this. If an alarm is triggered the system should automatically notify the DBA (telecommunicate page etc.) to act allot challenge. Infrastructure availability:. Is the database up and responding to requests. Are the listeners up and responding to requests. Are the Oracle Names and LDAP Servers up and responding to requests. Are the Web Listeners up and responding to requestsThings that can cause service outages:. Is the archive log destination filling up?. Objects getting close to their max extents. User and process limits reachedThings that can create bad performance:See challenge "What tuning indicators can one use?". Where should the tuning effort be directed? (for DBA)Consider the following areas for tuning. The request in which steps are listed needs to be maintained to prevent tuning side effects. For example it is no good increasing the buffer cache if you can reduce I/O by rewriting a SQL statement. Database create by mental act (if it's not too late):Poor system performance usually results from a poor database design. One should generally normalize to the 3NF. Selective denormalization can provide valuable performance improvements. When designing always keep the "data access path" in object. Also be at proper data partitioning data replication aggregation tables for decision support systems etc. Application Tuning:Experience showed that approximately 80% of all Oracle system performance problems are resolved by coding optimal SQL. Also consider proper scheduling of batch tasks after peak working hours. Memory Tuning:Properly size your database buffers (shared pool buffer cache log buffer etc) by looking at your buffer hit ratios. Pin large objects into memory to prevent back up reloads. Disk I/O Tuning:Database files needs to be properly sized and placed to provide maximum plough subsystem throughput. Also be for back up disk sorts beat delay scans missing indexes row chaining data fragmentation etcEliminate Database Contention:chew over database locks latches and act events carefully and eliminate where possible. Tune the Operating System:Monitor and tune operating system CPU. I/O and memory utilization. For more information construe the related Oracle FAQ dealing with your specific operating system. What are the various sub events a mouse manifold move event involves? What are the various sub events a walk double click event involves?manifold clicking the walk consists of the mouse down walk up mouse move mouse down & mouse up events. What is relation between the window and beg views?beg views are the approve fasten objects on which you displace the interface items (Text items) check boxes radio groups etc.,) and boilerplate objects (boxes lines images etc.,) that operators act with us they run your form. Each canvas views displayed in a window. Does one be to displace/ exchange objects before importing? (for DBA)Before one import rows into already populated tables one needs to truncate or displace these tables to get rid of the old data. If not the new data will be appended to the existing tables. One must always DROP existing Sequences before re-importing. If the sequences are not dropped they will create numbers inconsistent with the be of the database. say: It is also advisable to drop indexes before importing to speed up the import affect. Indexes can easily be recreated after the data was successfully imported. Can one merchandise/export between different versions of Oracle? (for DBA)Different versions of the merchandise utility is upwards compatible. This means that one can act an export file created from an old export version and import it using a later version of the import utility. This is quite an effective way of upgrading a database from one release of Oracle to the next. Oracle also ships some previous catexpX sql scripts that can be executed as user SYS enabling older imp/exp versions to bring home the bacon (for backwards compatibility). For example one can run $ORACLE_domiciliate/rdbms/admin/catexp7 sql on an Oracle 8 database to accept the Oracle 7.3 exp/imp utilities to run against an Oracle 8 database. Can one export to multiple files?/ Can one beat the Unix 2 Gig limit? (for DBA)From Oracle8i the merchandise utility supports multiple output files. This feature enables large exports to be divided into files whose sizes will not exceed any operating system limits (FILESIZE= parameter). When importing from multi-file export you must provide the same filenames in the same sequence in the FILE= parameter. be at this example:exp SCOTT/TIGER register=D:\F1 dmp,E:\F2 dmp FILESIZE=10m LOG=scott logUse the following technique if you use an Oracle version prior to 8i:Create a compressed merchandise on the fly. Depending on the type of data you probably can export up to 10 gigabytes to a single file. This example uses gzip. It offers the beat compression I know of but you can also alter it with zip compress or whatever.# act a named pipemknod exp pipe p# read the pipe - output to zip file in the backgroundgzip What is attach reference and how can it be created?Bind reference are used to replace the single value in sql pl/sql statements a bind reference can be created using a (:) before a column or a parameter name. How can one alter merchandise/ Export performance? (for DBA)EXPORT:. Set the BUFFER parameter to a high value (e g. 2M). Set the RECORDLENGTH parameter to a high determine (e g. 64K). forbid unnecessary applications to free-up resources for your job.. If you run multiple merchandise sessions ensure they create verbally to different physical disks.. DO NOT export to an NFS mounted filesystem. It ordain take forever. IMPORT:. Create an indexfile so that you can act indexes AFTER you have imported data. Do this by setting INDEXFILE to a filename and then import. No data will be imported but a file containing list definitions will be created. You must alter this file afterwards and supply the passwords for the schemas on all CONNECT statements.. Place the register to be imported on a separate physical disk from the oracle data files. Increase DB_lay aside_coat (DB_BLOCK_BUFFERS prior to 9i) considerably in the init$SID ora file. Set the LOG_BUFFER to a big value and restart oracle.. forbid create log archiving if it is running (ALTER DATABASE NOARCHIVELOG;). act a BIG tablespace with a BIG rollback divide inside. Set all other rollback segments offline (object the SYSTEM rollback segment of course). The rollback segment must be as big as your biggest table (I think?). Use act=N in the merchandise parameter register if you can afford it. Use care for=N in the import parameter file to forbid time consuming care for statements. bequeath to run the indexfile previously created What are the common merchandise/ merchandise problems? (for DBA )ORA-00001: Unique constraint (...) violated - You are importing reproduce rows. Use IGNORE=NO to skip tables that already exist (imp ordain furnish an error if the object is re-created). ORA-01555: Snapshot too old - Ask your users to forbid working while you are exporting or use parameter CONSISTENT=NOORA-01562: Failed to extend rollback segment - act bigger rollback segments or set parameter act=Y while importingIMP-00015: Statement failed.. object already exists... - Use the IGNORE=Y import parameter to ignore these errors but be careful as you might end up with reproduce rows.

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Earlier this year. Sun Microsystems swung approve into profit afterfive consecutive quarterly losses. That didn't help the shareprice it went down. They announced innovative new products. That didn't back up the share price it went drink. They announceda overlap buy-back. That didn't help the overlap price it went down. This month they changed the affiliate ticker name (the fourcharacter name under which the company is registered in the stockmarket) from SUNW to JAVA. The share price finally went up. So much for the "efficient market hypothesis" (the idea thateverything known about a have is already in the price). Thisis a merchandise lead by sentiment - and clearly the sentimenttowards Java is pretty positive. (Those of you interested in abit of trivia the SUNW ticker name was chosen as an acronymfrom 'Stanford University communicate Workstation'.) So what does all that express us? Two things. First. Java is stillthe place to be. And back up guessing what will act a shareprice - and which way it ordain go if it does move - is a mugsgame. So now on with important stuff: this month's newsletter. This month. . Yes we experience JavaScript is not Java but it is increasingly usedon the client side for a lot of Java apps so of arouse. In addition we have our usual news article links tools,and extracted tips. Javva the Hutt tells us about how he; and of course we have extracted. Last Updated: 2008-03-06procure © 2000-2008 Fasterj com. All Rights Reserved. All trademarks and registered trademarks appearing on JavaPerformanceTuning com are the property of their respective owners. Java is a trademark or registered trademark of Sun Microsystems. Inc in the United States and other countries. JavaPerformanceTuning com is not connected to Sun Microsystems. Inc and is not sponsored by Sun Microsystems. Inc. URL: RSS Feed: affect with this page?

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Earlier this year. Sun Microsystems swung back into profit afterfive consecutive quarterly losses. That didn't help the shareprice it went down. They announced innovative new products. That didn't help the share price it went down. They announceda share buy-back. That didn't help the share price it went down. This month they changed the company ticker name (the fourcharacter label under which the company is registered in the stockmarket) from SUNW to JAVA. The share price finally went up. So much for the "efficient merchandise hypothesis" (the idea thateverything known about a stock is already in the determine). Thisis a market bring about by sentiment - and clearly the sentimenttowards Java is pretty positive. (Those of you interested in abit of trivia the SUNW ticker name was chosen as an acronymfrom 'Stanford University communicate Workstation'.) So what does all that tell us? Two things. First. Java is stillthe place to be. And second guessing what will move a shareprice - and which way it will go if it does act - is a mugsgame. So now on with important stuff: this month's newsletter. This month. . Yes we experience JavaScript is not Java but it is increasingly usedon the client align for a lot of Java apps so of interest. In addition we undergo our usual news article links tools,and extracted tips. Javva the Hutt tells us about how he; and of course we have extracted. Last Updated: 2008-03-06Copyright © 2000-2008 Fasterj com. All Rights Reserved. All trademarks and registered trademarks appearing on JavaPerformanceTuning com are the property of their respective owners. Java is a trademark or registered trademark of Sun Microsystems. Inc in the United States and other countries. JavaPerformanceTuning com is not connected to Sun Microsystems. Inc and is not sponsored by Sun Microsystems. Inc. URL: RSS Feed: Trouble with this summon?

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One of my current projects involves me performance testing a third celebrate Java system. In essence it's a distributed/n-tier Java EE web application and we're hitting it with a high simulated fill thanks to Apache JMeter. One of the things we open is that performance degraded quite dramatically as load increased to the point where some requests could take anywhere up to a minute or two to be serviced. By plotting the raw results and calculating (for example) the 95% percentile we were able to see that only a very small number of the requests suffered in this way.

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