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DB2 9 for z/OS: Using the Utilities Suite

7.4.3 Using SLIDING SCALE
One of the things that is difficult for a user when using compressed table spaces is estimating a good size for the PRIQTY and SECQTY quantities before the LOAD. When using the sliding scale algorithm, this is no longer necessary. Just specify PRIQTY=-1 and SECQTY=-1 or omit the PRIQTY and SECQTY values during the CREATE TABLESPACE and CREATE INDEX statements and make sure that the subsystem parameter OPTIMIZE EXTENT SIZING or MGEXTSZ on installation panel DSNTIP7 is set to YES.
When MSGEXTSZ=YES, DB2 will allocate the DB2 extents using a sliding scale algorithm. The primary extent will be allocated with a default value (1 CYL for non-LOB table spaces and indexes, 10 CYLS for LOB table spaces). The secondary extents will be allocated with an increased size. This function is also called autonomic DB2 space allocation. The algorithm helps to reduce the number of wasted space and improves the user productivity.
For more information about space allocations and the sliding scale algorithm, refer to DB2 Version 9.1 for z/OS Administration Guide, SC18-9840 and the IBM Redpapers™ publication IBM System p5 520 and 520Q Technical Overview and Introduction, REDP-4137.