LOGBUFF configuration parameter

Use the LOGBUFF configuration parameter to specify the size in kilobytes for the three logical-log buffers in shared memory.

onconfig.std value
LOGBUFF 64
units
Kilobytes
values
An integer in the range of 32 - (32767 * pagesize / 1024), where pagesize is the default system page size. The value must be evenly divisible by the default system page size. If the value is not evenly divisible by the page size, the database server rounds down the size to the nearest value that is evenly divisible by the page size.
takes effect
After you edit your onconfig file and restart the database server.

Usage

The three logical log buffers permit user threads to write to the active buffer while one of the other buffers is being flushed to disk. If flushing is not complete by the time the active buffer fills, the user thread begins writing to the third buffer.

If the RTO_SERVER_RESTART configuration parameter is enabled, set the value of the LOGBUFF configuration parameter to 256 kilobytes. If the value of the LOGBUFF configuration parameter is less than 256 kilobytes, a warning message displays when you restart the server.

Otherwise, set the value of the LOGBUFF configuration parameter to 32 kilobytes for standard workloads or 64 kilobytes for heavy workloads. The database server uses the LOGBUFF parameter to set the size of internal buffers that are used during recovery. If you set LOGBUFF too high, the database server can run out of memory and shut down during recovery.

If you log user data in smart large objects, increase the size of the log buffer to make the system more efficient. The database server logs only the portion of a smart-large-object page that changed.

You can view information about the logical log buffers by running the onstat -l command.


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