Over coming the 4 GB limit of VSAM.

[Angel]

Hello,

Does anyone know a way to come around the 4 GB limitation while defining a LINEAR cluster? Note these volumes are not managed my SMS.

Thanks for any help!

[Robert Sample]

Use the DATACLASS attribute of the DEFINE CLUSTER. The value to use for DATACLASS, however, MUST be provided by someone working at your site as different sites use different values.

[Angel]

But DATCLASS is part of SMS setup?

[enrico-sorichetti]

But DATCLASS is part of SMS setup?

That' s the reason the people to ask are those in Your storage support
THEY implemented the rules for Your SMS setup

[Robert Sample]

If you read the manual on DEFINE CLUSTER, you will discover that the manual EXPLICITLY states that DATACLASS can be used for SMS or non-SMS managed storage. Yes, it is part of SMS but it can also be used outside SMS.

[Angel]

I have suggested to use the Extended Format (VSAM EF) files. As I read about them, they allow to add an extra 32 control bytes to each data block. But they need to be DFSMS managed. It seems to solve the problem. So even if a DATACLASS is also given the restriction of 4GB anyways remains, right?

[Robert Sample]

This is another reason you REALLY need to talk to your site support group. If the DATACLASS given does not support VSAM extended format (a DATACLASS can be used for different reasons), then yes the 4 GB limit still applies. Only someone working at your site can provide you with the site-specific information you need on how to get your VSAM data set to go past 4 GB; we can only say that yes it can be done.

[Angel]

This is another reason you REALLY need to talk to your site support group.  If the DATACLASS given does not support VSAM extended format (a DATACLASS can be used for different reasons), then yes the 4 GB limit still applies.  Only someone working at your site can provide you with the site-specific information you need on how to get your VSAM data set to go past 4 GB; we can only say that yes it can be done.

We ended up using 4 GB limit, as going beyond that was not recommended by the policies.

[Robert Sample]

We ended up using 4 GB limit, as going beyond that was not recommended by the policies.

Policies often wind up being in effect long after they should have been changed.  I've used a number of VSAM linear and KSDS data sets as large as 60 GB with no problems; a policy against them makes less and less sense as time passes.