Owner(s):

How do I check my VSAM data set?
If you have any doubts about the structural integrity of the index and data components, you can use the command: EXAMINE IDCAMS. This will return with problems if there are any. The output will be one of the IDCxxxxx messages, where the x's will be replaced by the code of the error.

Look in MVS System Messages, Volume 3 (GDE - IEB) for the explanation for these messages.

What are some common VSAM problems?

Below is a list of some of the most common VSAM problem. Each one will be accompanied by the questions, 'How did this happen?' and 'What do I do for recovery?'

Lack of virtual storage:
Error Message format: IDC3351I VSAM{OPEN|CLOSE|I/O}
    • can be 136, 132, or 40.
How did this happen?
An abend occurs due to the lack of virtual storage; one of two things happened:
-VSAM data set is being accessed by a subsystem as CICS
-VSAM data set is being accessed by your program

What do I do for recovery?
In the first case, CICS was performing the synchpoint and journaling, and will be able to recover the data by rolling it back.
In the second case, try re-running the program, or restoring your backup and then re-run the job.


Initial loading problems:
Error Message format: IDC3308IDuplicate Record, or IDC3351I VSAM {Open|Close|I/O}
    • can be 8, 12, or 116.
How did this happen?
You attempted to store a record with a duplicate key, or you used the unique key
option is on with a duplicate record, or you attempted to sot a record in skip- sequential mode out of ascending key sequence.

What do I do for recovery?
In the first case, there is no need for recovery because the data is saved in the
the input file. The program needs to be sorted and re-run.


Structural Damage:
Error Message format: IDC3351I VSAM {Open|Close|I/O}
    • can be 8, 12, or 116.
How did this happen?
Because KSDS or VRRDS VSAM data sets are organized with an index, they
can fail more easily and in more ways than other data sets. If any pointers become corrupt, the data can be lost or duplicated.
What do I do for recovery?
It is crucial that the EXAMINE command is run on the data set as soon as
possible because some damage can cause further breakage until the original
diagnosis may be impossible to determine. Once this command is run, a possible solution could be to read the data in physical sequential mode through its data component. Refer to 3.4.4, Broken Index scenario for more details.

How do I backup my VSAM Data Sets?

It is important to back up data by using methods such as using the SMS management class with ABARS for backups. This will allow a restore of your data in the cases of hardware errors and application errors. You can also make a remote copy for disaster recovery. The BWO -Backup While Open- allows a logical dump for an IMS or CICS/VSAM data set while it is open.
When you define a cluster with IDCAMS, you must declare it with a BWO. The options for BWO are

TYPECICS
For RLS processing, this will activate BWO for CICS. In non RLS processing, CICS will determine whether to use BWO of the specification in CICS control data named FCT.

TYPEIMS
Use this parameter to enable BWP processing in an IMS environment.

NO
This parameter is for situations when BWO does not apply to the cluster.

How do I keep my system maintained?

Maintaining a VSAM data set involves a few categories.
  • Reorganization: VSAM uses a new DASD storage technology which implements: numerous high-capacity, small-size FBA, SCSI/SSA disks; redundancy in different types of RAID; large amounts of cache, mainly to avoid the write penalty caused by RAID; plenty of microcode in order to support RAID, cache algorithms, the mapping between the disks and the logical 3390/3380 volumes (as seen by z/OS), and in the RVA case, the virtualization of the 3390/3380.
  • VSAM data sharing: "To protect the integrity of your VSAM data sets, VSAM uses internal locks and issues ENQs in SYSVSAM major name, which invokes the MVS Enqueue Manager routine to serialize the resource locally. To serialize the full cluster across systems, it is required to have the Global Resource Serialization (GRS) or an equivalent product with the caution of not placing SYSVSAM resource name in RNL exclusion list.
Some of the consequences of placing SYSVSAM in the exclusion list include: loss of records, overlaid records, duplicate records, invalid index structures, invalid catalog records, invalid data set dumps, backups, restores, or migrations, incorrect extends of the data set, and incorrect release of space in the data set."(ibm.com/redbooks)
  • Extended Addressability: the main idea in the extended addressability is to make applications transparent to the function.

To keep your system maintained, apply PTF selective services in your operating system, especially the ones associated with VSAM. Use the search word “dsbreaker” to find fixes associated with broken VSAM data sets.

Where can I find more information?

If you need more information, visit the VSAM Knowledge Database. This interactive, question and answer diagnostic tool should be able to get you the answer you need. This database can be found at http://knowledge.storage.ibm.com/