Thanks to the folks who gave me info on Unidata triggers. I've had those
implemented for years and they do work very simply and well. Universe has
been a whole different ballgame.
It turns out that Universe has cleverly adapted the triggers from SQL. I
say cleverly because it probably really is on some esoteric mathematical
level. And certain from a viewpoint of 'using what you have'. But for an
old Pickie like me it has been very foreign. Also they have made use of the
Begin Transaction business - so that the writes can be rolled back using
that existing logic, I reckon. Again, good re-use. But this is also an area
that I'm not familiar with.
The three problems that I had were with:
1) The SB+ COMMON block - this was resolved by adding $OPTIONS PICK to the
trigger program - and to all the programs down the line that it called.
2) WRITES requiring locks: The Begin Transaction relies on a system variable
called ISOMODE which can be set to 0,1 or 2 to control how rigorous the
locking requirements are - as part of the 'transaction/rollback' stuff. I
was able to get my programs working by making sure I had a READU before each
WRITE (which I didn't have in some cases - where I had decided in my own
wisdom that it was safe not to do it - audit logs, new items, etc.) but I
can't get into the SB+ code and the authors thereof were also of this same
wisdom. But it turned out that by using Uniadmin to set ISOMODE to 0, this
problem was alleviated.
3) Last, I wanted to be able to control whether the write should occur. I
can do it - the manual was not clear on the syntax and I kept thinking there
was something more, but apparently as long as I put:
DUMMY = SetDiagnostics("This message is about why the item cannot be
written"), the trigger will fail the write and display that message. I don't
display that message, I don't use the variable DUMMY, I don't set any
particular flag. The display and the failure to write is not pretty.
4) One thing I cannot overcome is that the triggers in Universe will not
permit any interaction. So my program can't explain to the user why it
doesn't think they should write and then allow them to make a decision. It
throws them back into their item, though, so I guess they can save the item
somewhere else or something from there.
Again, thanks to Manu in particular who has obviously fought the exact same
battle - and to those of you who offered up the "how to" in Unidata. You
are so lucky you are doing it in Unidata!
Hope this helps someone else, some day.
Susan Joslyn
SJ+ Systems Associates, Inc.
PRC(r) Complete software development life-cycle management for U2.
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