Oracle Standby Implementation Tantra Invedy

Standby Database Introduction Fail over Solution Disaster Recovery Solution if remote Ease of implementation Minimum impact on Production System Read Only Standby Database

Fail Over and Disaster Recovery Solution Unplanned Outage Protection Primary host or machine failure or any physical outage Catastrophic failures such as fire, blizzard, earthquake Database corruption if detected in time Possible planned outage solution OS upgrade or maintenance. Fail over and fall back capabilities.

Ease of Implementation and minimum impact Basic recovery skills needed to maintain Oracle standby Archiving, transferring files, restoring files, recovery Very little impact on production database Only need to transfer archive files

New 8i Read only Standby Provide ability to query standby database Mutual exclusive from standby recovery Can not write to data files or online redo logs

Disadvantages Standby Database disadvantages  Lack of utilization, Cost, Not Scalable.  Non-logging operations are not propagated.  Potentially 2+ log files behind the production database. Can be minimized by mirroring redo log files.

Alternative Solutions Options  Hardware Fail Over (Fail Over)  OPS on Oracle 8i or RAC on Oracle 9i (Fail Over / Scalability)  Oracle 9i Logical Standby (Fail Over / DR)  EMC SRDF (Fail Over / DR)

Standby DB Architecture Understanding Logging and Non- Logging Operation  Any data modification / structural change is recorded in Oracle redo log files.  For performance reason, some operation can perform no logging operation. (index rebuild, Direct path load, CTAS)

Server Process Datafiles Log Buffer Buffer Cache Shared Pool Redo logs Archived logs LGWRDBWR ARC0

Standby DB Architecture Primary Database in Archivelog Mode  Archives are shipped to Standby site  Locally managed temporary tablespace (allows standby to be open read only) Standby Database in Recovery Mode  Applies archives  Independent from the production database

Standby DB Architecture Control will be updated from information contained in redo log files RFS will consume all of IO from primary Database archiver, then create archive files and update control file Recovery process will wake up every 15 seconds, look for archives to apply

Overview of Managed Oracle Standby DB Primary control file Standby control file Primary DBStandby DB Primary Instance Standby Instance Redo log Arc log ARCH RFS DBWR Recovery proc Arc log Net8

Activate Standby Database Open Read-Only Mode Recovery process is suspended when DB is in read only mode Activate Standby Database Resets online redo logs Pre-Clear online redo logs Incompatible with production Database

Refresh Standby Database Refresh entire Standby Database if Loss of any archive logs Production database undergoes a resetlogs operation Refresh parts of the standby database if No logging operation is performed Media corruption of certain standby datafiles

Refresh Standby database Controlfile Refresh of standby controlfile if Production controlfile is recreated with new parameter Standby controlfile is corrupted or destroyed

Consideration on Oracle Standby implementation On unplanned outage, data in online redo logs might be loss. Time to fail over depends on resetlogs operation. Only activate standby database in case of an emergency. Once activated the new primary does not have a standby database.

Consideration on Oracle Standby implementation Avoid no logging operations, as it corrupts the datafile on standby. Read only mode is mutually exclusive from Database recovery. It is a DR solution if implemented remotely.

Safeguarding Standby implementation Monitor Alert log files on both primary and standby databases Running a job to trigger online redo log switch at certain interval. Monitor archive log transfer status. Monitor no logging operations. Scripted procedures to rebuild standby. Perform thorough testing.

Testing before production deployment Creation of standby database Activation of standby database Performance of archive log transfer under heavy load. Maintenance of any structural changes on primary database. Failing back after activation of standby.

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