When restoring objects from libraries that have a large number of objects and the save was done via a parallel save, it is possible performance will be affected if using more than 4 devices (7.1 and below) or 12 devices (7.2 and above) were used.
At release 7.1, BRMS can only track starting positions for up to 4 parallel tape files. it does not specify starting positions for any additional tape files. The RSTOBJ command, which BRMS uses under the cover, requires starting positions to be specified for all of the tape files, otherwise the default search from the beginning of all tape files is used. It takes a long time to search through millions of tape blocks for the desired data. For 7.1, saves should be limited to a maximum of 4 parallel resources if specific objects are frequently restored from very large libraries.
BRMS release 7.2 includes several improvements when starting position is used to locate data in a tape media file. If a save was done with Object Level Detail and the data was saved at 7.2 or later, one of the improvements will utilize tape file starting position for up to 12 parallel resources.