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Oracle internals, debugging and undocumented features

Category Archives: HA

Snapshot Standby

Converting physical standby to snapshot standby

Depens on Data guard configuration change protection mode:

On Primary database:
SQL> ALTER DATABASE SET STANDBY DATABASE TO MAXIMIZE  PERFORMANCE ;
SQL>  alter system archive log current;

Use these queries to check synchronization between primary and standby:

Primary: SQL> select thread#, max(sequence#) “Last Primary Seq Generated”
from v$archived_log val, v$database vdb
where val.resetlogs_change# = vdb.resetlogs_change#
group by thread# order by 1;

PhyStdby:SQL> select thread#, max(sequence#) “Last Standby Seq Received”
from v$archived_log val, v$database vdb
where val.resetlogs_change# = vdb.resetlogs_change#
group by thread# order by 1;

PhyStdby:SQL>select thread#, max(sequence#) “Last Standby Seq Applied”
from v$archived_log val, v$database vdb
where val.resetlogs_change# = vdb.resetlogs_change#
and val.applied=’YES’
group by thread# order by 1;

Stop logs shipment on primary database:
ALTER SYSTEM SET log_archive_dest_state_2=’DEFER’ SCOPE=BOTH SID=’*’;

On Physical Standby:

On an Oracle Real Applications Cluster (RAC) database, shut down all but one instance.

Stop Redo Apply on standby , if it is active.

SQL> ALTER DATABASE RECOVER MANAGED STANDBY DATABASE CANCEL;

Ensure that the database is mounted, but not open.

SQL> ALTER DATABASE CONVERT TO SNAPSHOT STANDBY;

SQL> ALTER DATABASE OPEN;

Check database status:

select database_role,open_mode from v$database;

Start all instances and database services

srvctl  start service -d <database_name> -s <service_name>

Reverting back to physical standby Read more of this post

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High Availability – Oracle GoldenGate

The GoldenGate ( now owned by Oracle Corporation ) for Active-Active solution provides  real-time bidirectional data movement between heterogeneous dual-active or multi-master databases. GoldenGate’s Active-Active solution also offers advanced features for data conflict detection and resolution.

KEY FEATURES:

  • Allows application transactions to be distributed across multiple databases
  • Provides full bi-directional data movement without distance constraints
  • Allows conflict detection and resolution
  • Enables sub-second latency even at high data volumes
  • Preserves transaction integrity for confidence in data across multiple active environments
  • Decouples source and target environments to support a wide variety of heterogeneous databases and platforms

 

Main page:

http://www.oracle.com/technology/products/goldengate/index.html

Documentation:

http://download.oracle.com/docs/cd/E15881_01/index.htm

Additional downloads from  Oracle E delivery site:

http://edelivery.oracle.com/EPD/Download/get_form?egroup_aru_number=11897207