Messages in the CA Datacom Multi-user (MUF) output log show that an Area that allowed for dynamic extend was extended during a data load but there were no x37 failure or messages. Messages in the MUF log:
DB01703I - DYNAMIC EXTEND OF AREA CBX00106 STARTED
DB01701I - DYNAMIC EXTEND OF AREA CBX00106 ENDED, TRACKS BEFORE 2,490 TRACKS AFTER 2,610
Also, a CXX report of the Area before the load showed statistics the Area with a single Table was only 13% full so there was plenty of room with no apparent reason.
Prior MUF failure.
z/OS and z/VSE
The dynamic extend occurred because the area free space index was inaccurate. This can occur as a result of a MUF failure since the free space index is maintained in memory and processed by the pipeline. The free space index is located in the IXX and Data buffers. If a MUF fails, both the free space index and the CXX statistics may no longer reflect what is actually in a data area.
If you experience this symptom, you can run DBUTLTY with RETIX KEYNAME=*DATA to repair the free space index and DBUTLTY with KEYNAME=*SETR to update the CXX statistics with a more accurate record count.
More information can be found in the CA Datacom/DB DBUTILTY Reference Guide 14.0 and above: Paragraph: Chapter 37: RETIX (Reconstruct Index)