Automatic Undo Management

The next topic presented will involve the Redo Logfile Advisor.

Redo Logfile Advisor

Oracle Database 10g introduces the Redo Logfile Advisor which determines the optimal smallest online redo log file size based on the current fast_start_mttr_target setting and mttr statistics. Therefore, setting up the fast_start_mttr_target parameter is necessary for enabling the advisor. It suggests an optimal value for the online redo log file and eliminates the need to determine optimal logfile sizes manually. An online redo logfile is considered to be of optimal size when it does not drive incremental checkpointing more than fast_start_mttr_target. The v$instance_recovery view has a new column for this value called OPTIMAL_LOGFILE_SIZE. Table 5.5 shows all the columns available in the v$instance_recovery view. The OPTIMAL_LOGFILE_SIZE column shows the redo logfile size in megabytes based on the current fast_start_mttr_target setting. All online redo log files should be set to this value or higher. 

Column	Data type
RECOVERY_ESTIMATED_IOS	NUMBER
ACTUAL_REDO_BLKS	NUMBER
TARGET_REDO_BLKS	NUMBER
LOG_FILE_SIZE_REDO_BLKS	NUMBER
LOG_CHKPT_TIMEOUT_REDO_BLKS	NUMBER
LOG_CHKPT_INTERVAL_REDO_BLKS	NUMBER
FAST_START_IO_TARGET_REDO_BLKS	NUMBER
TARGET_MTTR	NUMBER
ESTIMATED_MTTR	NUMBER
CKPT_BLOCK_WRITES	NUMBER