Max size of a LDS dataset

gylbharat · Posted: Fri Jul 19, 2013 9:55 pm

Hi,

What is the max LDS data set size which can be created in MVS? I thought the limit was 4GB? but I see a LDS data set having 12GB.

Robert Sample · Posted: Fri Jul 19, 2013 11:04 pm

The VSAM Demystified Redbook states on page 33 that a linear data set may be extended, so the 4 GB limit would not apply to an extended format LDS.

Anuj Dhawan · Posted: Sat Jul 20, 2013 12:12 am

And did you mean zOS? MVS is older than my age ...

gylbharat · Posted: Mon Jul 22, 2013 3:39 pm

Thanks Bob.

Nic Clouston · Posted: Mon Jul 22, 2013 5:17 pm

No "Bob" has entered this discussion!

dick scherrer · Posted: Mon Jul 22, 2013 8:24 pm

Hello,

gylbharat · Posted: Tue Jul 23, 2013 1:59 pm

Sure.

Pete Wilson · Posted: Mon Jul 29, 2013 6:58 pm

And LDS can be much larger than 4GB if you have assigned a Dataclas that has the Extended Addressability attribute. The 4GB is actually a VSAM size limit that applies unless you have the Dataclas that has the Extended Addressability attribute (and Extended Format). The only limit then is the number of allowable extents for VSAM (251) which another Dataclas attribute called Extent Constraint Removal deals with, and if Extent Constraint Removal is in effect the limit 7257 extents.

With a Dataclas that provides both the Extended Format and Extended Addressability and Extent Constraint Removal attributes the dataset can potentially be primary size+(secondary times 122 per volume), times 59 volumes. So depending on the size of the volumes it can be a vast amount.

gylbharat · Posted: Tue Jul 30, 2013 2:33 pm

Thanks Pete for the detailed information.

I have a question, if the LDS datasets are DB2 managed then how/where we can define the dataclass attribute? Is there any Zparm for that?

Pete Wilson · Posted: Tue Jul 30, 2013 2:51 pm

I'm not sure if it's in ZPARMS or if it's an option when defining an individual Table.

You can ask your Storage team if they would set it up in the SMS Dataclas ACS routines to automatically assign the appropriate Dataclas to your dataset (or a generic dataset mask), and also create the Dataclas if
there isn't already one with the required attributes available.

sushanth bobby · Posted: Tue Jul 30, 2013 3:59 pm

Gylbharat,

For non-partition tablespaces max size is 64GB, so you will have 32 datasets of 2GB size.
For partition tablespace, each dataset size is limited by DSSIZE parameter. Options available are 1G 2G 4G 8G 16G 32G 64G

Max Size of table DB2 currently supports is 128TB(2048 Partition x 64GB datasets)
More information in SQL Reference in CREATE TABLESPACE

If you want to mention dataclas, check CREATE STOGROUP in SQL Reference

Thanks,
Sushanth

Pete Wilson · Posted: Tue Jul 30, 2013 6:26 pm

Thanks Sushant, I'll crib that bit of info!

The other issue is TIOT limitations if the tables are spread over too many volumes I believe. (i.e. about 4k of TIOT used for every volume). May not be such an issue now with XTIOT.