Recommended Redolog size

[Former Member]

Dear all,

I want to check the advised redolog size on my server. I know Oracle 10g has an option for this, and this by using  FAST_START_MTTR_TARGET  parameter.

For now I have:

SQL> show parameter mttr_target 

NAME TYPE VALUE

------------------------------------ ----------- ------------------------------

fast_start_mttr_target integer 0

SQL> select optimal_logfile_size from v$instance_recovery; 

OPTIMAL_LOGFILE_SIZE

--------------------

Without setting fast_start_mttr_target to a value different to 0, the Redo Logfile Size Advisor won't give you any advice about the optimal size (in MB.) for the redo logfile.

The default is 300 seconds (5 Minutes). and maximum we can give 3600 ( 1 Hour).

But how can I decide which value to give to fast_start_mttr_target ?

Can you please advise ?

Thank you,

Jordy

[paul_power]

Hi Jordy,

There is not an exact recommendatio as it deoends on the system usage.

See SAP Notes

79341    Checkpoint not complete

1068186  "checkpoint not complete" message increasingly in alert file

"

Increasing the size of the redo log files is particularly useful

if there are small time frames between the log switches (< 1

minute during peak load). The disadvantage of big redo log files

is the lower checkpoint frequency and the longer time Oracle

needs for an instance recovery.

"

Regarding fast_start_mttr_target

If FAST_START_MTTR_TARGET is specified, LOG_CHECKPOINT_INTERVAL should
not be set or set to 0.

A general rule of thumb is to switch logs at most every twenty minutes.

See SAP Note 793113 FAQ: Oracle I/O configuration

Regards,

Paul