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

SAS/ACCESS Interface to Teradata 4 Examples 835users update or insert into the table, they can lock you out from reading the table.In this situation, you want to reduce the isolation level during a read operation. Todo this, you specify these read SAS/ACCESS lock options and values.3 READ_ISOLATION_LEVEL=ACCESS3 READ_LOCK_TYPE=TABLE3 READ_MODE_WAIT=YESOne of these situations can result from the options and settings in this situation:3 Specify ACCESS locking, eliminating a lock out of yourself and other users.Because ACCESS can return inconsistent results to a table reader, specifyACCESS only if you are casually browsing data, not if you require precisedata.3 Change the scope of the lock from row-level to the entire table.3 Request that Teradata wait if it attempts to secure your lock and finds theresource already locked.3 Use SAS/ACCESS lock options to avoid contention.When you read or update a table, contention can occur: the DBMS is waiting forother users to release their locks on the table that you want to access. Thiscontention suspends your SAS/ACCESS session. In this situation, to avoidcontention during a read operation, you specify these SAS/ACCESS read lockoptions and values.3 READ_ISOLATION_LEVEL=READ3 READ_LOCK_TYPE=TABLE3 READ_MODE_WAIT=NOOne of these situations can result from the options and settings in this situation.3 Specify a READ lock.3 Change the scope of the lock. Because SAS/ACCESS does not support row lockingwhen you obtain the lock requested, you lock the entire table until your readoperation finishes.3 Tell SAS/ACCESS to fail the job step if Teradata cannot immediately obtain theREAD lock.ExamplesSetting the Isolation Level to ACCESS for Teradata Tables/* This generates a quick survey of unusual customer purchases. */libname cust teradata user=testuser password=testpassREAD_ISOLATION_LEVEL=ACCESSREAD_LOCK_TYPE=TABLEREAD_MODE_WAIT=YESCONNECTION=UNIQUE;proc print data=cust.purchases(where= (bill1000));run;