Friday, April 13, 2007

RMAN Enhancement ( Oracle 11g New Features)

Oracle 11g RMAN Enhancement( Oracle 11g New Features )
  • Enhanced configuration of archive deletion policies
    Archive can be deleted , if it is not need DG , Streams Flashback etc
    When you CONFIGURE an archived log deletion policy applies to all archiving destinations, including the flash recovery area. BACKUP ... DELETE INPUT and DELETE... ARCHIVELOG use this configuration, as does the flash recovery area. When we back up the recovery area, RMAN can fail over to other archived redo log destinations if the flash recovery area is inaccessible.
  • Configuring backup compression
    In 11g can use CONFIGURE command to choose between the BZIP2 and ZLIB compression algorithms for RMAN backups.
  • Active Database Duplication
    Now DUPLICATE command is network aware i.e.we can create a duplicate or standby database over the network without taking backup or using old backup.
  • Parallel backup and restore for very large files
    RMAN Backups of large data files now use multiple parallel server processes to efficiently distribute theworkload for each file. This features improves the performance of backups.
  • Improved block media recovery performance
    RECOVER command can recover individual data blocks.
    RMAN take older, uncorrupted blocks from flashback and the RMAN can use these blocks, thereby speeding up block media recovery.
  • Fast incremental backups on physical standby database
    in 11g we can enable block change tracking on a physical standby database (ALTER DATABASE ENABLE/DISABLE BLOCK CHANGE TRACKING SQL statement).This new 11g feature enables faster
    incremental backups on a physical standby database than in previous releases.because RMAN identifywe the changed blocks sincethe last incremental backup.

Thursday, April 12, 2007

Oracle 11g Compression of redo

Virag Sharma

Archived redo file can be compressed , while transfering to standby database

alter system set log_archive_dest_1='SERVICE=standby1


check where there compression is enabled or not

select dest_name , compression from v$archive_dest

compression column will show enable if it is enable.

Wednesday, April 11, 2007

Oracle 11g Online Query Capability of Physical Standby Database

Online Query Capability of Physical Standby Database( Oracle 11g New Features)

It is now possible to query a physical standby database while Redo Apply is active.This new capability increases your return on investment in Data Guard technology because a physical standby database can now be used to offload queries from the primary database in addition to providing data protection.

( We can do same with logical standby , what is diffrent here , well redo apply method is faster in physical stand by ie redo apply methode is diffrent in physical standby)

  • Stop log apply

    Alter database recover managed standby database cancel;
  • open database for read-only access

    alter database open
  • Once daabase open start redo apply

    alter database recover managed standby database
    using current logfile disconnect from session;

Tuesday, April 10, 2007

Automatic Memory Management( Oracle 11g New Features)

Automatic Memory Management ( Oracle 11g New Features)

Well in 10g SGA can be auto tune and 11g it extended to PGA as well ie SGA and PGA both can auto tune
( i would say , i understood this much only
11g memory management = SGA auto tune + PGA auto tune )

For auto memory, we need to set parameter MEMORY_TARGET and MEMORY_MAX_TARGET. Parameter MEMORY_TARGET is dynamic, we can change the target memory size at any time without restarting the database. The MEMORY_MAX_TARGET serves as an upper limit so that we cannot by mistake set the MEMORY_TARGET size too high. Because certain SGA components eithercannot easily shrink or must remain at a minimum size, the database also prevents you from setting thetarget memory size too low.

If MEMORY_TARGET is set to a non-zero value:

  • If SGA_TARGET and PGA_AGGREGATE_TARGET are set, they will be considered the min value for the sizes of SGA and the PGA respectively. MEMORY_TARGET can take values from SGA_TARGET + PGA_AGGREGATE_TARGET to MEMORY_MAX_SIZE.
  • If SGA_TARGET is set and PGA_AGGREGATE_TARGET is not set, we will still auto-tune both parameters. PGA_AGGREGATE_TARGET will be initialized to a value of (MEMORY_TARGET-SGA_TARGET).
  • If PGA_AGGREGATE_TARGET is set and SGA_TARGET is not set, we will still auto-tune both parameters. SGA_TARGET will be initialized to a value of min(MEMORY_TARGET-PGA_AGGREGATE_TARGET, SGA_MAX_SIZE (if set by the user)) and will auto-tune subcomps.

Monday, April 9, 2007

Oracle 11g Invisible Indexes

Invisible Indexes ( Oracle 11g New Features)

One can create Invisible Indexes to test performance or convert existing index into Invisible Indexe to check impact.
Optimizer not consider invisible indexes , we need to specify explicity with hint.Making an index invisible is an alternative to making it unusable or dropping it. Unlike unusable indexes, invisible indexes are maintained during DML statements.

CREATE INDEX I_emp_ename ON emp(ename)




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