A user table space is defined with DSSIZE 0, by default that's 2 Gig, but somehow PDA is showing 4 gig? Why?
PDAs RAIX_PIECESIZE and RATS_DSSIZE represent the TRUE dataset size. The DB2 catalog does not always. They had 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 .
I have included the IBM definitions below for an easy reference.
In the IBM v9 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)