Dual logging

We can configure WebSphere MQ to run with either single logging or dual logging. With single logging, log records are written once to an active log data set. With dual logging, each log record is written to two different active log data sets. Dual logging minimizes the likelihood of data loss problems during restart. If possible, the two log data sets should be on separate volumes. This reduces the risk of them both being lost if one of the volumes is corrupted or destroyed. If both copies of the log are lost, the probability of data loss is high.

Note:

You should always use dual logging and dual BSDSs rather than dual writing to DASD.

Single logging gives you 2 through 31 active log data sets, whereas dual logging gives you 4 through 62. Each active log data set is a single-volume, single-extent VSAM linear data set (LDS).

Although the minimum number of log data sets required is three, in practice you should have at least four, and on a busy system you might need more. This is to allow time for each log data set to be copied to archive before it is reused in the active log cycle.