Purging JAMS history is normally completely automated. When JAMS is initially installed, a job named JAMS_PURGE is created which is scheduled to run every Sunday. This job purges the JAMS History and then does a CONVERT/RECLAIM on the HIST.DAT file to reclaim space from the deleted records.
Verify that the JAMS_PURGE job is successfully running.
If JAMS_PURGE is running, it may be that a user is keeping more history than desired. Users can adjust the default values for the parameters to JAMS_PURGE to change the amount of history a user keeps.
It may also be that the HIST.DAT file grew so large because of an unusual event and the file is mostly free space. The JAMS_PURGE job won't shrink the physical size of the file. To shrink the file while preserving the history, perform the following:
$ MCR JAMS_EXE:JAMS_MASTER STOP SCHEDULE/NORESTART $ SET DEFAULT JAMS_DATA: $ ANALYZE/RMS/FDL/OUTPUT=HISTOPT.FDL HIST.DAT $ EDIT/FDL/NOINTERACTIVE/ANALYSIS=HISTOPT.FDL HISTOPT.FDL $ CONVERT/FDL=HISTOPT.FDL/STATS/NOSORT HIST.DAT HIST.DAT $ PURGE HIST.DAT $ MCR JAMS_EXE:JAMS_MASTER START SCHEDULE
Note: This may take a long time. If you don't need to retain the history and simply need to shrink it, the following can be utilized:
$ MCR JAMS_EXE:JAMS_MASTER STOP SCHEDULE/NORESTART $ SET DEFAULT JAMS_DATA: $ DELETE HIST.DAT;* $ CREATE/FDL=HIST.FDL HIST.DAT $ MCR JAMS_EXE:JAMS_MASTER START SCHEDULE