Log Reads

When DB2 has to read from the log, it is important that the reads perform well because reads are typically performed during recovery, restarts, and rollbacks. An input buffer must be dedicated for every process requesting a log read. DB2 first looks for the record in the log output buffer. If DB2 finds the record, it can apply it directly from the output buffer. If the record is not in the output buffer, DB2 looks for it in the active log data set and then in the archive log data set. When the record is found, it is moved to the input buffer so it can be read by the requesting process.

You can monitor the successes of reads from the output buffers and active logs in the statistics report. These reads are the better performers. If the record has to be read in from the archive log, the processing time is extended. For this reason, it is important to have large output buffers and active logs.