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On 07 Nov 2012 18:17, Nathan Andelin wrote:
I'm not settled on this technique, I just put it out for thought. It
appears that you can add table columns without "agonizing" about
"recompiling the world".

It seems to me that it would be much easier to just implement logical independence so that only the programs that need to use the new column would be changed and recompiled; changed to use the new LF which now includes the new column added to the PF. All other programs would remain unchanged, continuing to use their unchanged LF [an LF which was never updated to include the new column irrespective of PF changed by ALTER TABLE, CHGPF SRCFILE(named), or even when the PF was re-created such that the LF had also been re-created from source]. That works because all of the LFs would have been defined with explicit fields instead of merely inheriting the record format from the PFILE specification, which ensures the logical independence from the physical changes.

Thus total freedom from the alluded "agonizing" is achieved for the minor cost of some extra logical files to manage, while maintaining any protection provided from level checking, and as Charles stated... also with the great benefit of no changes to the other programs and their LF(s) which effectively eliminates the need for re-testing those other programs.

FWiW with regard to the subject, my opinion is that Level Checking is only as useful as a helmet might be for riding. In either case there is no value provided whenever no situation arose such that the protection offered would be required. Anyone who can correctly predict that no such situation will arise has no need for any assistance from a preventive. Also FWiW, failing to ensure a change to a record format effects an actual change to the Level Identifier [it is just a hash] when there has been a change [that could cause data issues], might be considered similar to failing to ensure a helmet is properly fastened; i.e. the best possible protection may not be afforded even though by appearances, the preventive seems enabled.


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