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11g(R1/R2) Data guard Enhancements Suresh Gandhi

11g(R1/R2) Data guard Enhancements Suresh Gandhi. Agenda. What is DATA GUARD ? Types of Data Guard Databases 11g Release 1 Enhancements 11g Release 2 Enhancements Active Data guard Snapshot Standby Database More Features Rolling Upgrade and Physical Standby Q&A. Data Guard Overview.

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11g(R1/R2) Data guard Enhancements Suresh Gandhi

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  1. 11g(R1/R2) Data guard EnhancementsSuresh Gandhi

  2. Agenda • What is DATA GUARD ? • Types of Data Guard Databases • 11g Release 1 Enhancements • 11g Release 2 Enhancements • Active Data guard • Snapshot Standby Database • More Features • Rolling Upgrade and Physical Standby • Q&A

  3. Data Guard Overview Data Guard Standby Plus more High Availability & Disaster Recovery Solution

  4. Provides ….

  5. Data guard Databases

  6. 11G R1 Enhancements Release 1 New Features

  7. R2 - Enhancements Release 2 New Features

  8. R2- New Features Release 2 New Features

  9. Active and Snapshot Standby Traditional Functionality until 10g 11g Snapshot Standby 11g Active DataGuard

  10. Active Data Guard Benefits

  11. Turn on Physical Standby to Active Standby Stop redo apply Database in standby mount mode Open readonly Open mode changed to read only Start the redo apply again using log file (SRL’s) Status changed to read only apply

  12. Turn on Physical Standby to Snapshot Standby Once sync check, convert standby to snapshot Open database Read write mode Need to close database Switched back to physical standby

  13. Additional Info – Active / Snapshot • WHAT OPERATION ALLOWED IN ACTIVE DATA GUARD ? • SELECT statements • Complex queries • Calling of stored procedures • Use of database links to redirect DML to Primary • Use of stored procedures to call remote stored procedures via database links • Use of SET ROLE • Use of ALTER SESSION and ALTER SYSTEM • No Datatypes restrictions like Logical Standby • Additional TEMPFILES can be created for Sorts • Flashback Query : SELECT … AS OF <SCN> • Additional License • SOME IMPORTANT POINTS FOR SNAPSHOT STANDBY DATABASE • PHYSICAL STANDBY DATABASE SHOULD BE IN FLASHBACK MODE • NO REAL TIME QUERY OR DATA • NO FAST START FAILOVER IN THIS MODE • NO SWITCHOVER/FAILOVER UNTIL CONVERTED TO PHYSICAL STANDBY • Free of Licence • POINTS • Configure the Flash Recovery Area • Set the Retention Target • Enable Flashback Database

  14. 10g Equivalent Snapshot commands Prepare the physical standby database to be activated SQL> ALTER SYSTEM SET DB_RECOVERY_FILE_DEST_SIZE=20G; SQL> ALTER SYSTEM SET DB_RECOVERY_FILE_DEST='/arch/oradata' Prepare the primary database to have the physical standby be diverged. Archive the current log file. SQL> ALTER SYSTEM ARCHIVE LOG CURRENT; Cancel Redo Apply and create a guaranteed restore point. SQL> ALTER DATABASE RECOVER MANAGED STANDBY DATABASE CANCEL; SQL> CREATE RESTORE POINT restore_pt GUARANTEE FLASHBACK DATABASE; Activate the physical standby database. SQL> ALTER DATABASE ACTIVATE STANDBY DATABASE; SQL> STARTUP MOUNT FORCE; SQL> ALTER DATABASE SET STANDBY DATABASE TO MAXIMIZE PERFORMANCE; SQL> ALTER DATABASE OPEN Revert the ac4vated database back to a physical standby database. SQL> STARTUP MOUNT FORCE; SQL> FLASHBACK DATABASE TO RESTORE POINT restore_pt; SQL> ALTER DATABASE CONVERT TO PHYSICAL STANDBY; SQL> STARTUP MOUNT FORCE;

  15. DATGUARD – Still More Features

  16. More Features – RMAN Active database Duplication • Steps • Create a pfile with only db_name=stby • Create directory structure for datafile locations • Create directory structure for dump locations • Create a password file (must match with target) • Listener & Tnsnames entries for new standby database • Startup nomount with pfile • Run the rman command in other box • Log File  RMAN> run { allocate channel prmy1 type disk; allocate channel prmy2 type disk; allocate channel prmy3 type disk; allocate channel prmy4 type disk; allocate auxiliary channel repstby type disk; duplicate target database for standby from active database spfile parameter_value_convert 'emrep','repstby' set db_unique_name='repstby' set db_file_name_convert='C:\','F:\' set log_file_name_convert='C:\','F:\' ; }

  17. More Features – Redo Compression • Requires Advanced Compression features • Compress redo as it is transmitted data • Automatically compress the data as it only resolves gaps • Helpful and useful in bandwidth constrained locations • Syntax:- • LOG_ARCHIVE_DEST_2=‘Service=stby Async compression=ENABLE’

  18. More Features – Heterogenous database support • Oracle 10g Dataguard support mixed environments 32bit and 64 bit configuration • Oracle 11G Dataguard supports mixed Windows/Linux in same configuration • Only Physical Standby • Same Endianess required on all platforms • Metalink : 413484.1

  19. More Features: Lost Write Detection • Due to hardware or storage issues lost writes can happen while transmission and blocks may be stale. • Very hard to diagnose in such of case of corruption • Feature:- • Compares version of Blocks • Between Standby blocks and redo stream • Version discrepancy can be either standby or primary • If Primary Database block corruption is detected  Resolved • Using standby failover and • Restore data consistency • New Initialization parameter • ALTER System set db_lost_write_protect = NONE/TYPICAL/FULL • 5% impact but increase protection

  20. More Features: Automatic Block recovery • 11g R2 automatically recovers corrupted blocks from standby copies of blocks • Automatic Block Media Recovery also automatically repair corrupted blocks discovered in the physical standby databases • Reduce recovery time in block corruption cases instead of restoring from tape or disks • RMAN command RECOVER BLOCK can be used for manual recovery and its check for all suitable or consistent blocks across several copies of backups or • Clause can be added RECOVER BLOCK … EXCLUDE STANDBY then wont check in standby • Automatic block recovery is applicable only in physical corruptions like • When checksum is invalid • Block contains all zeros • Block header is fractured

  21. More Features: Redo Flush • Yes, Redo can be flushed • Can be done when the primary is in mount mode • To avoid minimal loss of data and allowed failover to be performed without data loss • Syntax:- • ALTER System FLUSH Redo to <target DB Name>

  22. More Features: Sync with Primary • New command • ALTER SESSION SYNC WITH PRIMARY • WAIT FOR STANDBY TO BE SYNCHRONIZED WITH PRIMARY • FAILS IF REDO APPLY OR REDO TRANSPORT IS OFF REPORT TRANSPORT AND APPLY LAGS

  23. More Features: STANDBY_MAX_DATA_DELAY

  24. More Features: ROLE Based services • Services can be created and start based on the database ROLE, viz a new addition sys_context (Database ROLE) • In R2 services can be attached via srvctl • Service can failover when using Cluster or Oracle restart • 11gR1 to use triggers based on Database role • Example Trigger

  25. Rolling Upgrade : Transient Logical Standby Physical standby must be converted to Logical Standby and uses Flashback as fall out plan Downtime for upgrade is only the SWITCHOVER TIME

  26. Finally, Monitoring Views • GAP_STATUS , additional column in v$archive_dest – GAP or NO GAP • V$dataguard_stats for transport/apply lag • V$REDO_DEST_RESP_HISTOGRAM • Useful when need to analyse network latencies by checking transport lag • V$STANDBY_EVENT_HISTOGRAM

  27. Thank you!Q & A Internal

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