SAS/ACCESS 9.2 for Relational Databases: Reference, Fourth Edition

SAS/ACCESS Interface to DB2 Under z/OS 4 Column Selection for MOD Partitioning 491Autopartitioning Scheme for DB2 Under z/OSOverviewAutopartitioning for SAS/ACCESS Interface to DB2 under z/OS is a modulo (MOD)method. Threaded reads for DB2 under z/OS involve a trade-off. A threaded read witheven distribution of rows across the threads substantially reduces elapsed time for yourSAS step. So your job completes in less time. This is positive for job turnaround time,particularly if your job needs to complete within a constrained period of time. However,threaded reads always increase the CPU time of your SAS job and the workload onDB2. If increasing CPU consumption or increasing DB2 workload for your job areunacceptable, you can turn threaded reads off by specifying DBSLICEPARM=NONE. Toturn off threaded reads for all SAS jobs, set DBSLICEPARM=NONE in the SASrestricted options table.For general information about this feature, see “Autopartitioning Techniques in SAS/ACCESS” on page 57.Autopartitioning RestrictionsSAS/ACCESS Interface to DB2 under z/OS places additional restrictions on thecolumns that you can use for the partitioning column during the autopartitioningphase. Here are the column types that you can partition.3 INTEGER3 SMALLINT3 DECIMAL3 You must confine eligible DECIMAL columns to an integer range—specifically,DECIMAL columns with precision that is less than 10. For example,DECIMAL(5,0) and DECIMAL(9,2) are eligible.Column Selection for MOD PartitioningIf multiple columns are eligible for partitioning, the engine queries the DB2 systemtables for information about identity columns and simple indexes. Based on theinformation about the identity columns, simple indexes, column types, and columnnullability, the partitioning column is selected in order by priority:1 Identity column2 Unique simple index: SHORT or INT, integral DECIMAL, and then nonintegralDECIMAL3 Nonunique simple index: SHORT or INT (NOT NULL), integral DECIMAL (NOTNULL), and then nonintegral DECIMAL (NOT NULL)4 Nonunique simple index: SHORT or INT (nullable), integral DECIMAL (nullable),and then nonintegral DECIMAL (nullable)5 SHORT or INT (NOT NULL), integral DECIMAL (NOT NULL), and thennonintegral DECIMAL (NOT NULL)6 SHORT or INT (nullable), integral DECIMAL (nullable), and then nonintegralDECIMAL (nullable)