1. Administrator's Guide
  2. Optimizing Performance
  3. Tuning Oracle 11g Databases for Financial Management
  4. How to Determine Memory Settings for Oracle Database Release 11g
  5. LOG_BUFFER Sizing

LOG_BUFFER Sizing

In the system view v$sysstat, the value for redo buffer allocation retries reflects the number of times a user process waits for space in the redo log buffer. This value should be near zero for a properly sized database. For example: 

select name, value
from v$sysstat 
where name = 'redo buffer allocation retries' 
NAME VALUE 
redo buffer allocation retries 1021967

If the log buffer has no space for updates, the database must wait and retry. In this example, the database has retried a total of 1,021,967 times. To improve performance, increase the LOG_BUFFER parameter value. This value is expressed in bytes and must be a multiple of the log block size value, which is the operating system block size. For the Oracle Hyperion Financial Management application, set LOG_BUFFER to a minimum of 8 MB, and then use the above query to monitor the performance and increase as necessary. If LOG_BUFFER needs to be increased, Oracle recommends growing it by 50% at a time.