DSSIZE value within Database Analyzer for Db2 for RAIX_PIECESIZE and RATS_DSSIZE

Products

• Database Analyzer for DB2 for z/OS

Issue/Introduction

Tablespace is defined with DSSIZE 0, by default that is 2 Gb, but somehow Database Analyzer for Db2 for z/OS (PDA) is showing 4 Gb.

Resolution

PDA RAIX_PIECESIZE and RATS_DSSIZE represent the TRUE dataset size. The DB2 catalog does not always. There were backward compatibility
issues and such to deal with PDA uses the real ones so that customers can rely on them. PDA defaults to the real size based on what they should end
up being according to IBM doc or our testing results of what Db2 does.

Included the IBM definitions below for an easy reference.
In the Db2 9 SQL ref Appendix. Additional information for Db2 SQL there is a table in the appendix that talks about the size of partitions (datasets).

"Maximum size of a partition (table space or index)"
For table spaces that are not defined with LARGE or a DSSIZE of 4 GB:
4 GB, for 1 to 4096 partitions . For table spaces that are defined with a DSSIZE greater than 4 GB:
64 GB, depending on the page size (for 1 to 256 partitions for 4 KB pages, for 1 to 512 partitions for 8
KB pages, for 1 to 1024 partitions for 16 KB pages, and 1 to 2048 partitions for 32 KB pages)