Oracle REDO

Check

Thread#: Can be any number (usually 1) as long as all logs for the instance have the same number. In a RAC environment the thread number must be unique for each instance across the cluster.
Group#: Number identifying a log and any multiplexed copies. i.e. all logs in group 1 will be multiplexed copies of each other. Each group needs to be identified by a different number.
Status: UNUSEDACTIVEUNASSIGNED
Type:ONLINESTANDBY

Resize

If your logfiles are too small (or too large), use the following process to resize them...

Run /u01/dba/oraredologs.sql to identify existing log files and repeat the steps below until all logs are the new size...

ALTER DATABASE DROP LOGFILE 'member';

If you encounter ORA-01623 (log 999 is current log for thread 999 - cannot drop) then perform a log switch...

ALTER SYSTEM SWITCH LOGFILE;

Add a new logfile with the new size and the same name as the logfile you just dropped...

ALTER DATABASE ADD LOGFILE 'member' SIZE 5M;

Review the values for the initialization parameters LOG_CHECKPOINT_INTERVAL and LOG_CHECKPOINT_TIMEOUT.

Initialization Parameters

LOG_CHECKPOINT_TIMEOUT

To switch logfile if log has not been switched for one hour...

ALTER SYSTEM SET LOG_CHECKPOINT_TIMEOUT=3600 SCOPE=BOTH;

LOG_CHECKPOINT_INTERVAL

TODO

Tuning Tips

Tips to reduce I/O waits...

The operations that contribute to the log file sync wait are:

Steps 2 and 3 are accumulated in the "redo write time" statisticStep 3 is the "log file parallel write" wait eventStep 5 and 6 may become significant as system load increases
In a Data Guard environment with SYNC transport, step 3 also includes the network write time and the write time to the Standby Redo Logs.

Bibliography