ARC0910E - DFSMShsm (MCDS|BCDS|OCDS) is Full

An HSM CDS is a key-sequenced data set (KSDS). The CDS space is partitioned into Control Areas. When a control area is full and a new record must be inserted, the control area is split. A portion of the control area moves to an empty cell.  When there are no empty control areas to split into, HSM indicates the CDS is full and issues an ARC0910E messages.  The CDS no longer has the ability to grow via a control area split.

The TOTAL FREESPACE field of a LISTCAT shows the total amount of space available in each control area.  It does not monitor how may empty control areas are available.

The PERCENT USED field of the LISTCAT is a better representation of the CDS's fullness. The PERCENT USED field represents the percentage of empty control areas. If LISTCAT reports that a CDS has a PERCENT USED of 72%, then 28% of the control areas are empty and available for splitting. The PERCENT FULL is determined by the ratio of the highest used RBA (HURBA) divided by the highest allocated RBA (HARBA). When these two values are equal, the HSM CDS is considered full.

Reorganizing the CDS completely fills each control area until all records are inserted.  Any record insertion into a full control area causes a split, reducing the number of empty control areas.  Control areas continue to split for most of the initial record insertions until no full control areas are full.  The initial flurry of control area splits causes the CDS to PERCENT FULL to level off at value that was reported before the reorganization. Increasing the size of the CDS is the proper recourse.

Although reorganizing the CDS provides temporary relief, the permanent fix action is to enlarge the CDS.