Locking SAS Data Objects

Types of Locks

The following types of locks can be used on a data object:

explicit lock: is set with the LOCK statement or the LOCK command for exclusive access to the data object type. The action of the LOCK statement or the LOCK command is restricted by the server engine, the object that is being accessed, and the way that the object is accessed (for example, a data set is locked for writing). For details, see The LOCK Statement and the LOCK Command.
implicit lock: is automatically set on the data object type as required by the SAS operation that is being executed. Each SAS operation has default locking requirements that are affected by two factors: the data object that is being accessed and the way that the object is accessed. For example, a DATA step that includes a MODIFY statement accesses an observation for update, by default.

Regardless of the type of lock that is attempted, in order to lock a selected data object, the server must lock preceding levels of the hierarchy, as needed. This type of lock is also referred to as an implicit lock.

When you specify a data object in a LOCK statement, you set an explicit lock on that object. If you lock a lower-level object without explicitly locking the higher level or levels, SAS locks the higher level (or levels) automatically.

For example, when you explicitly lock a SAS data set (lower-level lock) but not the SAS library (higher-level lock) that contains it, the data library is locked implicitly. An implicit lock allows other users to access the locked data library, even though you have exclusive access to the locked data set.

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