The PRIMARY KEY integrity constraint includes both the NOT NULL and UNIQUE constraints.

To initiate an audit on an existing SAS data set with the DATASETS procedure, you specify the data set in the AUDIT statement, and then you specify the INITIATE statement. You specify the library with the LIB= option.

In the MODIFY statement, you specify the master data set followed by the transaction data set. Then you specify the key variable in the BY statement.

The value of _IORC_ is a numeric return code that indicates the status of the most recently executed I/O operation. Checking the value of this variable allows you to detect abnormal I/O conditions and direct execution in particular ways.

In the MODIFY statement, you list the SAS data set that you want to modify. Then you use the IC CREATE statement to create the integrity constraint. This integrity constraint is a CHECK constraint with a WHERE clause to specify the condition that the variable values must meet.

The MODIFY statement in a DATA step can be used only to modify the values in a data set. It cannot be used to modify the descriptor portion of the data set.

Audit trails are used to track changes that are made to a data set in place.

You use the DATASETS procedure and the MODIFY statement to specify a number of generation data sets for a data set. The GENMAX= option is used to specify the number of versions to save. The number you specify includes the base version.

When you use the KEY= option, you must specify the update that you want to make to the data set.

The keyword ALL is used to indicate that you want to delete all generations of the specified data set, including the base version. The keyword HIST deletes the generation data sets, but saves the base version.