Red Alert - z/OS V2R2 - Potential for z/OS V2R2 JES2 (HJE77A0) members unable to WARM start

Last week there were two important recommendations for z/OS V2R2 users. Here's the info on the first one. I'm just taking over the text from the Red Alert.

Abstract #1:

Potential for z/OS V2R2 JES2 (HJE77A0) members unable to WARM start.

Users Affected:

Systems running z/OS V2R2 that have the JES2 Checkpoint residing on DASD -and- running in DUAL mode (CKPTDEF MODE=DUAL)

Description:

For systems that meet the above criteria, JES2 uses a change log to contain a summary of updates since the previous checkpoint cycle. JES2 may encounter I/O errors ($HASP291) and/or abends (S18A) when attempting to read in a large valid checkpoint change log. A checkpoint I/O reconfiguration will be triggered in this case, however potential overlays of JES2 private storage from the original error may result in unpredictable errors after exiting the reconfiguration.
Any z/OS V2R2 JES2 member in the multi-access spool (MAS) will not be able to read the checkpoint containing a large valid change log without encountering abends. z/OS V2R1 JES2 members in the MAS will be able to read the checkpoint appropriately, but the z/OS V2R2 members will not be able to WARM start. If the entire MAS is comprised of z/OS V2R2 members, then no member will be able to process the checkpoint and this may result in a required COLD start.
Please see APAR OA51558 for additional details.

Recommended Actions:

For users that meet the above criteria, checkpoint should be switched to DUPLEX mode (CKPTDEF MODE=DUPLEX) to avoid the situation.

If you haven't signed up to the Red Alerts by now, you really should do it. Just go over here.