misi01
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Joined: 02 Dec 2002
Posts: 629
Topics: 176
Location: Stockholm, Sweden
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 Posted: Sun Aug 21, 2022 5:55 am Post subject: IMS, DL/1 and DB2 positioning |
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Background
We are running IMS and converting DL/1 programs to DB2.
One of the programs is a 3270 one using the usual MFS panel.
The program ONLY reads the DL/1 database.
The logic in the program is approximately this:
| Code: | S100:
perform read-mid
if PF3-equivalent, leave
perform process-input
perform write-mod
go to S100 |
(the program was written in 1984 !!!!)
The program allows the user to scroll left/right by 4 DL/1 segments at a time.
One of the aspects of it that has puzzled me is the following.
Assume this scenario: -
Users sees first 4 segments (1-4). Presses PF11 to see 5-8.
The first thing the program does is to do a GU on the root, then read "past" the first 4
after which reads segments 5-8 and presents them
I can see that, having done a GU on the root, it has to read "past" previous segments to
get to its starting point, but my first question would be. is the GU necessary, or is
it a case that IMS might have/has swapped the program out, and as a result, when it's swapped
back in, the child position has been lost?
Now, to the equivalent DB2 cursor code. I saw some interesting links on declaring a cursor as scrollable (never used it myself).
- does it work in IMS and do I need to declare the cursor as FOR HOLD?
- is IMS potentially swapping the program in and out goint to be a problem such that the cursor is lost?
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Michael |
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