SQL> ALTER DATABASE FORCE LOGGING;

This statement can take a considerable amount of time to complete, because it waits for all unlogged direct write I/O to finish.

3.1.2 Create a Password File

Create a password file if one does not already exist. Every database in a Data Guard configuration must use a password file, and the password for the SYS user must be identical on every system for redo data transmission to succeed. SeeOracle Database Administrator's Guide.

3.1.3 Configure a Standby Redo Log

A standby redo log is required for the maximum protection and maximum availability modes and the LGWR ASYNC transport mode is recommended for all databases. Data Guard can recover and apply more redo data from a standby redo log than from archived redo log files alone. You should plan the standby redo log configuration and create all required log groups and group members when you create the standby database. For increased availability, consider multiplexing the standby redo log files, similar to the way that online redo log files are multiplexed.

Perform the following steps to configure the standby redo log.

Step 1 Ensure log file sizes are identical on the primary and standby databases.

The size of the current standby redo log files must exactly match the size of the current primary database online redo log files. For example, if the primary database uses two online redo log groups whose log files are 200K, then the standby redo log groups should also have log file sizes of 200K.

Step 2 Determine the appropriate number of standby redo log file groups.

Minimally, the configuration should have one more standby redo log file group than the number of online redo log file groups on the primary database. However, therecommendednumber of standby redo log file groups is dependent on the number of threads on the primary database. Use the following equation to determine an appropriate number of standby redo log file groups:

( maximum number of logfiles for each thread + 1) * maximum number of threads

Using this equation reduces the likelihood that the primary instance’s log writer (LGWR) process will be blocked because a standby redo log file cannot be allocated on the standby database. For example, if the primary database has 2 log files for each thread and 2 threads, then 6 standby redo log file groups are needed on the standby database.

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Note: Logical standby databases may require more standby redo log files (or additional ARCnprocesses) depending on the workload. This is because logical standby databases also write to online redo log files, which take precedence over standby redo log files. Thus, the standby redo log files may not be archived as quickly as the online redo log files. Also, seeSection 5.7.3.1.

Step 3 Verify related database parameters and settings.

Verify the values used for the MAXLOGFILESandMAXLOGMEMBERSclauses on the SQLCREATE DATABASEstatement will not limit the number of standby redo log file groups and members that you can add. The only way to override the limits specified by theMAXLOGFILESandMAXLOGMEMBERSclauses is to re-create the primary

database or control file. How to know the number of these two types of parameters’?

alter database backup controlfile to trace as '$ORACLE_HOME/dbs/control.bak';

Step 4 Create standby redo log file groups.