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

Threaded Reads 4 Options That Affect Threaded Reads 53data reads, numerical algorithms, and data analysis in threads. Only some SASprocedures are threaded applications. Here is a basic example of PROC REG, a SASthreaded application:libname lib oracle user=scott password=tiger;proc reg simpledata=lib.salesdata (keep=salesnumber maxsales);var _all_;run;For DBMSs, many more SAS steps can become eligible for a threaded read,specifically, steps with a read-only table. A libref has the form Lib.DbTable, where Libis a SAS libref that "points" to DBMS data, and DbTable is a DBMS table. Here aresample read-only tables for which threaded reads can be turned on:libname lib oracle user=scott password=tiger;proc print data=lib.dbtable;run;data local;set lib.families;where gender="F";run;An eligible SAS step can require user assistance to actually perform threaded reads.If SAS cannot automatically generate a partitioning WHERE clause or otherwiseperform threaded reads, the user can code an option that supplies partitioning. Todetermine whether SAS can automatically generate a partitioning WHERE clause, usethe SASTRACE= and SASTRACELOC= system options.Threaded reads can be turned off altogether. This eliminates additional DBMSactivity associated with SAS threaded reads, such as additional DBMS connections andmultiple SQL statements.Threaded reads are not supported for the Pass-Through Facility, in which you codeyour own DBMS-specific SQL that is passed directly to the DBMS for processing.Options That Affect Threaded ReadsFor threaded reads from DBMSs, SAS/ACCESS provides these data set options:DBLICE= and DBSLICEPARM=.DBSLICE= applies only to a table reference. You can use it to code your ownWHERE clauses to partition table data across threads, and it is useful when you arefamiliar with your table data. For example, if your DBMS table has a CHAR(1) columnGender and your clients are approximately half female, Gender equally partitions thetable into two parts. Here is an example:proc print data=lib.dbtable (dbslice=("gender=’f’" "gender=’m’"));where dbcol>1000;run;SAS creates two threads and about half of the data is delivered in parallel on eachconnection.When applying DBSLICEPARM=ALL instead of DBSLICE=, SAS attempts to"autopartition" the table for you. With the default DBSLICEPARM=THREADED_APPSsetting, SAS automatically attempts threaded reads only for SAS threaded applications,which are SAS procedures that thread I/O and numeric operations.DBSLICEPARM=ALL extends threaded reads to more SAS procedures, specifically