Re: SQL Mass Delete Vs. READ/DELETE

Joe,

Hee hee! (oiling up the torches, getting out the pitchforks)


Just last week I think I came across a difference between the methods which
surprised me. A nightly purge was using SQL to perform a DELETE on sets of
records, because as you say, SQL shines at this and it was the perfect tool
for the job. Its been that way for years in this jobstream.

Because of an unrelated user error, we decided to go back and undelete a few
records to examine the previous contents of them. The machine is on V5R4,
so needs to use UNDEL2 instead of the patched older UNDELM program, but I
don't think that is related to the issue.

On the file where we used SQL DELETE, the deleted records did not have any
recoverable contents. All fields were at the default values; character
fields were blank, numerics were zero, dates were 01/01/0001, etc. For
files where we did not use SQL DELETE, we could see and recover the contents
of deleted records.

So it appears like SQL must also wipe the contents of records as it deletes
them. Maybe this was anecdotal and due to something else. I didn't run
additional tests to see what happened, but it did mean we couldn't use
UNDEL2 to examine the contents.

Not that I'd say having the ability to undelete is a legitimate reason to
not use SQL -- I have no plans on quit using SQL for this. I just found it
interesting.

Doug