Locking SAS Data Objects

Defaults for Selected SAS Operations

Knowledge of the default data objects and how they are accessed will help you to anticipate the results from specific operations when you write your application or issue SAS statements in interactive mode. Defaults for Selected SAS Operations shows the defaults for some frequently used SAS operations when locking is executed.

Defaults for Selected SAS Operations
SAS Operation				What the Data Object Is Locked For	The Data Object Locked (Default)
DATA step
	DATA statement
			without MODIFY statement	Output	Member
			with MODIFY statement	Update	Observation
	SET statement
			without POINT= and KEY= options	Input	Observation
			with POINT= and KEY= options	Input	Member
	MERGE statement			Input	Observation
	MODIFY statement
			without POINT= and KEY= options	Update	Observation
			with POINT= and KEY= options	Update	Member
	UPDATE statement			Input	Observation
Procedures
	APPEND procedure
		BASE= option		Update	Member* or observation
		DATA= option		Input	Observation
	COPY procedure
		IN= option		Input	Observation
		IN= option with MOVE option		Output	Observation
		OUT= option		Output	Member
	FSBROWSE procedure
		DATA= option		Input	Observation
	FSEDIT procedure
		DATA= option		Update	Observation
	FSVIEW procedure
		DATA= option without EDIT option		Input	Observation
		DATA= option with EDIT option		Update	Observation
	PRINT procedure
		DATA= option		Input	Observation
		UNIFORM= option		Input	Member
	SORT procedure
		DATA= option		Input	Observation
		OUT= option		Output	Member
	SQL procedure
		CREATE TABLE statement		Output	Member
		DELETE statement		Update	Observation
		INSERT statement		Update	Member
		UPDATE statement		Update	Member
* If no other tasks are currently accessing the BASE= data set, then PROC APPEND opens the data set with a member lock.

Changing the Data Set Option Default Object

In some SAS operations, you can change the SAS data set option default object. When the syntax of a statement or a command allows you to specify SAS data set options, you can use the CNTLLEV= option to override the default object and to specify the object that you want. For example, in a SET statement that contains the POINT= option, you can change the default from member to observation by specifying the CNTLLEV= data set option. In this example, the value, REC (for record), means the same as observation.

set datalib.fuel (cntllev=rec) point=obsnum;

Note: If you make this change, the values in a specific observation might differ each time that you read the observation. [cautionend]

You can also change the data object observation to member. You might do this to ensure that a data set does not change while you are processing it. For example, if you use a SET statement with a BY statement and you cannot use an index to retrieve the observations in sorted order, you can use the CNTLLEV= option to reset the data object observation to member.

set datalib.fuel (cntllev=mem);
by area;

In some SAS operations, you cannot override the default setting because the statement or the command requires it. For example, a DATA statement requires a member setting when the MODIFY statement is omitted from the DATA step. Without the MODIFY statement, the data set that is specified in the DATA statement must be opened for output. Therefore, even if you specify CNTLLEV=REC in such a DATA statement, the DATA step tries to set the data object as member, but this will fail if other operations are accessing the data set.

Note: Be careful when using the CNTLLEV= option in a procedure. Some procedures make multiple passes through an input data set and require that the data remains the same to guarantee the integrity of the output. If a procedure has this requirement, a warning is issued but the procedure will allow its objects to be reset if you use the CNTLLEV= option. [cautionend]

For details about the syntax of the CNTLLEV= option in the SET statement, see the CNTLLEV= data set option in SAS Language Reference: Dictionary.

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