Sizing the redolog

Question

My redolog details are below,
SQL> COLUMN value FORMAT 999,999,999,990
SQL> COLUMN name FORMAT a31
SQL> SELECT a.name,b.value
2 FROM v$statname a,v$sysstat b
3 WHERE a.statistic# = b.statistic#
4 AND a.name like '%redo%';
NAME VALUE
redo synch writes 281,602
redo synch time 27,625
redo blocks read for recovery 0
redo entries 24,978,833
redo size 9,970,044,216
redo buffer allocation retries 27,380
redo wastage 36,843,120
redo writer latching time 21
redo writes 141,083
redo blocks written 20,073,539
redo write time 346,493
NAME VALUE
redo log space requests 347,823
redo log space wait time 63,510
redo log switch interrupts 0
redo ordering marks 617,362
redo subscn max counts 740,460
16 rows selected.
SQL>
SQL>
I see that the redolog space request is high. I resized the redolog by 125m but still shows that the space request parameter has not changed. I dropped the redolog files and resized it to 125m. What i should do to reduce the space request close to 0?

Answer 1

Why increase log_buffer?There is a direct correlation between "redo log space requests" and a too-small log_buffer.
The Oracle Documentation notes:
"The redo log space requests Oracle metric indicates the active log file is full and Oracle is waiting for disk space to be allocated for the redo log entries. Space is created by performing a log switch.
Small Log files in relation to the size of the SGA or the commit rate of the work load can cause problems. When the log switch occurs, Oracle must ensure that all committed dirty buffers are written to disk before switching to a new log file. If you have a large SGA full of dirty buffers and small redo log files, a log switch must wait for DBWR to write dirty buffers to disk before continuing.
http://www.dba-oracle.com/t_log_buffer_optimal_size.htm
MetaLink note 216205.1 Database Initialization Parameters for Oracle Applications 11i, recommends a log_buffer size of 10 megabytes for Oracle Applications, a typical online database:
A value of 10MB for the log buffer is a reasonable value for Oracle Applications and it represents a balance between concurrent programs and online users.
The value of log_buffer must be a multiple of redo block size, normally 512 bytes.
Hope this helps. . .
Donald K. Burleson
Oracle Press author
Author of "Oracle Tuning: The Definitive Reference":
http://www.dba-oracle.com/bp/s_oracle_tuning_book.htm