IDD and reversing DMCL changes

Discussion created by ca.portal.admin on Jun 3, 2007
Latest reply on Jun 4, 2007 by ca.portal.admin
Hi all,

When making DMCL changes in preparation for a ""Space
Maintenance Release"", occasionally we have to defer the
implementation. So then we reverse the DMCL changes by
(re-)modifying both the Segment & the DMCL, and genning the
DMCL. NB: Basically we convert it back to what it was
previously. And it can be a time-consuming process.

However, I came up with a ""new method"" of doing this quickly;
ie: backup the IDD catalog component (3 datasets), before
making any DMCL changes.
And if we have to roll-back, I just simply restore the IDD
Catalog. And it seems to work sweet. (NB: Have only used this
in the test region).

However, the senior DBA is uncomfortable with this, as he is
unsure what it might affect.

Can someone please shed some light on this, as to whether it is
an okay thing to do. All feedback gratefully received.

NB: As a comparable practise - our production IDD migration
procedure is done by copying the IDD Base Component (2
datasets) from the Acceptance environment to the Production
environment, and it has been done this way for many years, with
no problems.

Thanks very much.
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Re: IDD and reversing DMCL changes
"You can also just punch out the to-be-affected areas and load them back
in with a batch IDD job if necessary. The only caveat here is if any of
the areas involved have been EXTENDED - if this is the case then you
have to load the area definition back in with the original number of
pages and perform the EXTEND SPACE online to bring the area back up to
its prior configuration, since extend specs in IDD are displayed as a
comment. PLUS, if you do not do this, you will not know immediately
that you have mis-defined the area. But the CALC algorithm will be
using the wrong page range, and you will start getting 0326 errors for
records that DO exist, and you will be allowed to ADD records defined as
""duplicates not allowed"" when they already DO exist, because the CALC
algorithm is telling IDMS to look on the wrong page . . . Been there,
done that. Not a pretty picture.

HOWEVER, given that I assume that you're restricting access to the CV
during your modifications to yourself alone, your method of performing a
physical (as opposed to logical) backup and restore of the IDD files via
a native OS utility should work fine - the only changes being reversed
with the restore should be those that you have made (and wish to
reverse). I do this kind of thing all the time. Just play it safe and
back up the files when the CV is down, and make sure that you are
backing up all physical aspects of the file from the OS' perspective -
such that you need not specify a DD (or DLBL for VSE) for the restore.
Otherwise you're asking for trouble.

Thus, given all of the above, I'd go with your method if you can.

Hopefully this information is helpful.

Mike Champagne