The JES spool space is segmented into Track Groups, usually 3 trks to a group. The track group is managed as a single entity when data is added to spool. The maximum number of track groups allowed is part of the JES initialization parameters.
When max track groups have been defined, no additional spool volumes may be added.
When all track groups are used, jobs needing spool space wait.
Also, F1 (HELP) will probably explain the fields on the panel.
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