All, We just learned that we have a problem with IAM (Innovation Access Method) the high perf replacement for VSAM. No idea how long it has been going on, and I have tickets open with both BMC and IBM on this. Seems to only affect IAM files, and exists in both z/OS V2.4, and V2.5, and multiple versions of IAM. We are currently at 10.x, but the problem occurs in V9.x as well. We see the problem mostly in our Development space, not in PROD (or nothing reported yet, but problem exists there too). We dont migrate much in PROD, and is why we havent had the problem reported there.
The scenario here is - existing IAM file gets updates, records added or updated, doesnt matter. - file goes unreferenced for 7 days, so HSM migrates - file gets recalled, the updates that were made are gone. In HSM we do have FSM enabled (Fast Subsequent Migration), where if HSM is called to migrate the dataset, and it hasnt changed since last migration, it just deletes the dataset and reconnects it to the already migrated version in HSM. We've learned that turning FSM off circumvents the problem. IBM tells us that "HSM checks the DS1RECAL and DS1IND08 flags in the Format-1 DSCB of a data set to determine if a data set is eligible for fast subsequent migration. The DS1RECAL flag is used to indicate if a data set has been recalled and the DS1IND08 flag is used to indicate if a data set been modified since it was last recalled. " IBM doc seems to indicate that OPEN handles setting these bits, BMC support says they arent messing with these bits. I dont know *who* is to blame. I'd be curious to hear from other installations that use IAM, has HSM with FSM turned on. The recreate scenario is (assumes new test file) with FSM turned on 1 - Allocate test IAM file and add a record easily identifiable 2 - HSM Migrate the file 3 - HSM Recall the file 4 - RECORD ADDED IN #1 is there. 5 - Add another record with new identifiable info 6 - HSM migrate the file. 7 - HSM Restore the file. 8 - Record from #1 is there, record from #4 is not there. With FSM turned off, the dataset gets fresh migration copy every time, so the issue is masked. ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to lists...@listserv.ua.edu with the message: INFO IBM-MAIN
