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

718 Performance Summary 4 Chapter 25Performing a threaded read on this table causes Oracle to make two separateconnections to the Oracle server. SAS tracing shows the SQL generated for eachconnection:data new;set x.EMPLOYEE(DBSLICPARM=ALL);run;ORACLE: SELECT "EMPNO", "EMPNAME", "HIREDATE", "SALARY", "GENDER"FROM EMPLOYEE WHERE ABS(MOD("EMPNO",2))=0ORACLE: SELECT "EMPNO", "EMPNAME", "HIREDATE", "SALARY", "GENDER"FROM EMPLOYEE WHERE ABS(MOD("EMPNO",2))=1EMPNO, the primary key, is selected as the MOD column.The success of MOD depends on the distribution of the values within the selectedModColumn and the value of N. Ideally, the rows are distributed evenly among thethreads.You can alter the N value by changing the second parameter of DBSLICEPARM=LIBNAME option.Performance SummaryThere are times you might not see an improvement in performance with the MODtechnique. It is possible that the engine might not be able to find a column thatqualifies as a good MOD column. In these situations, you can explicitly specifyDBSLICE= data set option to force a threaded read and improve performance.It is a good policy to let the engine autopartition and intervene with DBSLICE= onlywhen necessary.Temporary Table Support for OracleFor general information about this feature, see “Temporary Table Support for SAS/ACCESS” on page 38.Establishing a Temporary TableA temporary table in Oracle persists just like a regular table, but contains eithersession-specific or transaction-specific data. Whether the data is session- ortransaction-specific is determined by what is specified with the ON COMMIT keywordwhen you create the temporary table.In the SAS context, you must use the LIBNAME option, CONNECTION=SHARED,before data in a temporary table persists over procedure and DATA step boundaries.Without this option, the temporary table persists but the data within it does not.For data to persist between explicit SQL pass-through boundaries, you must use theLIBNAME option, CONNECTION=GLOBAL.If you have a SAS data set and you want to join it with an Oracle table to generate areport, the join normally occurs in SAS. However, using a temporary table you can alsohave the join occur on the Oracle server.