Planning your archive storage

This section describes the different ways of maintaining your archive log data sets.

We can place archive log data sets on standard-label tapes, or DASD, and we can manage them by data facility hierarchical storage manager (DFHSM). Each z/OS logical record in an archive log data set is a VSAM control interval from the active log data set. The block size is a multiple of 4 KB.

Archive log data sets are dynamically allocated, with names chosen by WebSphere MQ. The data set name prefix, block size, unit name, and DASD sizes needed for such allocations are specified in the system parameter module. We can also choose, at installation time, to have WebSphere MQ add a date and time to the archive log data set name.

It is not possible to choose specific volumes for new archive logs. If allocation errors occur, off-loading is postponed until the next time off-loading is triggered.

If you specify dual archive logs at installation time, each log control interval retrieved from the active log is written to two archive log data sets. The log records that are contained in the pair of archive log data sets are identical, but the end-of-volume points are not synchronized for multivolume data sets.