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OracleApprender avatar image
OracleApprender asked

Explain FORCE LOGGING feature in 9i ?

Can anyone explain me how the FORCE LOGGING feature will work in the Oracle version 9i. Appreciated for the help in advance. Thank you.

oraclerecoverylogging
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KillerDBA avatar image
KillerDBA answered

I found a discussion of that here:

iDevelopment on Data Guard

The rest of this is an extract from their discussion that focuses on FORCE LOGGING...

You should place the primary database in FORCE LOGGING mode. This option is a new feature with Oracle Release 9.2 and will override any user transaction that attempts to specify NOLOGGING. If a user were able to perform NOLOGGING operations on the primary database would mean that some changes would not be fully logged within the redo stream to maintain the standby database. Any unlogged operations would invalidate the standby database and would require substantial DBA intervention in order to manually propagate unlogged operations. By placing the primary database in force logging mode, nologging operations are still permitted to run without error, but the changes will will be placed into the redo stream anyways. You can use the following statement to place the primary database in force logging mode:

SQL> alter database force logging;
Database altered.

The above statement may take a substantial amount of time to complete. The database must want for all unlogged direct write I/O operations to finish.

You can use this to find out if a database is in force loggin mode:

SQL> select force_logging from v$database;

FORCE_LOGGING
-------------
YES
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OracleApprender avatar image
OracleApprender answered

By setting FORCE LOGGING to TRUE, all transactions will generate REDO. This is used for Data Guard, so no data will be missed (i.e. transactions that were run with NOLOGGING option in Standby database). For more description we can refer the KillerDBA's answer, which is more descriptive.

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