With z/OS 1.4 we now will adjust the index CISIZE if VSAM determines what the user has specified is too small to describe the entire data CA?.There is no way to prevent this from occurring and there are no warning messages to indicate VSAM has done this....You also cannot prevent the redefinition of these datasets when they are copied or recalled using HSM.Setting aside the almost unbelievable arrogance of overriding people's coded parameters without even a warning message: Is there anything we can do to prevent this? Or at least get some kind of warning when, hours, days or months after the z/OS upgrade, a file is altered when it is redefined or migrated in?
Or are we stuck with running IBM's unsupported tool, INDXCISZ, against every VSAM file in our shop, including recovering all the migrated ones?
Without meaning to diminish your concerns, perhaps the reason IBM does not issue a warning message is that they changed the calculations of how they override CISIZE settings, not whether or not they override the settings. In appropriate situations, they have always overrode CIZISE settings. What they did in z/OS (Release 3, actually) was just to change the settings they set CISIZE to when they override your settings; IBM has never issued a warning message when they override a CISIZE setting.
However, I'm speculating on IBM's reasons, and you should contact them for a specific answer. And as you will see, they did make note of this in the z/OS Migration Guide, and in SHARE presentations both they and Cheryl Watson made.
I don't know how you use the INDXCISZ tool, so I don't know if you will need to use that. Understanding how DFSMS sets CISIZE and reviewing your IDCAMS source when you redefine a data set may be sufficient to resolve this issue. Hopefully the aforementioned Q&A will answer your questions. If not, please contact me with remaining questions after you've reviewed this answer.
CISIZE may be overridden whenever you delete and redefine a VSAM file, so you should review any situations in your installation where this may happen.
This was first published in December 2005