IBM Mainframe Forum

Is there an easy way of finding out the highest key currently in use in a KSDS? I'm trying to implement a simple "Add new record" function in <advertising removed>. In my test data Custf is a VSAM file keyed on Custf.Account, and I'm trying to work out the COBOL that I want for a NewKey function in


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If Custf were SQL I'd be able to use SELECT MAX(Account) FROM ..., and if STARTBR offered an DESC order option I could browse to the last record, but it doesn't. Setting Account = 999999 and then EXEC CICS STARTBR (which would immediately ENDFILE) wouldn't return the last record (would it?). So what's my best approach?

Thank you,
Robert Barnes

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Sorry everybody, I was too quick to post. The answer (which was obvious when I read further) was
STARTBR with RIDFLD value of X'FF'
then
READPREV

Duh!

Robert

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And what is going to happen when two users do that around about the same time?

BillyBoyo, thank you for your comment, but won't it be OK here? The logic is


The reference to Custf.$LastKey [creates COBOL code that] performs a paragraph that reverse-browses Custf to determine the largest value of Custf.Account. Adding 1 to it creates the next free key, and then GET custf KEY(CustF.Account) UPDATE; reads and locks this record. There is no user interaction between the two Jazz statements so there is very little time for another user to have created a record with this key, but it is not impossible. However, as the error message indicates, this GET is not permitted to find an existing record, so that if the record does exist because the improbable has actually happened the update, which occurs at the END GET, will fail because it's attempting to WRITE rather than REWRITE.

For the update case the logic is: -

You'll notice that here the GET has the option CHECKSUM, which will compare the value returned in the input message (field IWSPG2.CheckSum-custf) with the value sent out with a CHECKSAVE option on the preceding Enquiry. Both CHECKSAVE and CHECKSUM use EXEC CICS BIF DIGEST to calculate a 40 hex character message digest.

Would you like me to send a copy of the generated COBOL? If yes, please send me a private email (e-mail address removed to reduce spamming) and I'll send you a sample of the generated code. I'd be delighted for you to look over it and give me feedback.

Regards, Robert.

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