How to update vsam file records?

Question

I want to read a VSAM file record using CICS commands and then update it using REWITE command, but I have two major problems:

1. throu readnext operation to access a vsam record, for some of the records, i need to access database and do some process there, finally commit database changes. But the thing is whenever I commit the database, the readnext encounters an error INVREC, which dosnt allow to access next records in VSAM file.
2. When accessing any record in VSAM file, I need to update the record in file, so I used REWRITE CMMAND, which returns error number 16.

Overall I want to do the following process: 1.Read a VSAM file records one by one using READNEXT comand 2. Access database and do commit 3. Rewrite the VSAM file record using REWRITE command.

Answer 1

The file itself needs to be defined with a log parameter and logstreamid if you want it to be forward recoverable. The CICS definition can then be changed to be RLS(YES).

Just to cover the bases, the CICS region also needs SIT Parameter RLS set to YES.

Answer 2

1. The Db2 COMMIT also causes a SYNCPOINT for CICS resources. As documented on the STARTBR command, "A browse can end by using the ENDBR, SYNCPOINT, or SYNCPOINT ROLLBACK commands. Also an implicit sync point at the end of task ends the browse." So once you issue the COMMIT for Db2, you must restart the browse by issuing a new STARTBR command.
2. You cannot issue a REWRITE command unless the READ (or READNEXT) specified the UPDATE option. READNEXT with UPDATE is only supported by VSAM files that were opened in RLS (Record Level Sharing) mode.

In your scenario you probably need to do the following:

• Issue STARTBR to start the browse of the VSAM file.
• Issue READNEXT to get the first VSAM record.
• Save the key of the record that was retrieved.
• Access the database
• Issue Db2 COMMIT or CICS SYNCPOINT
• Issue READ UPDATE for the record key that was saved
• Issue REWRITE for the file
• Issue STARTBR with the saved key.
• Issue READNEXT
• If record returned is the one just updated, issue READNEXT to get the next record.
• Loop back to the SQL statement to access the database.