SAS Companion for the OpenVMS Operating Environment

Multiuser Access to SAS Files

Under certain circumstances, a SAS file can be accessed by more than one user concurrently. This feature enables different users, or the same user from different processes, to access the same SAS file at the same time without conflict. However, to prevent problems of integrity or data conflict, multiple accesses of data are sometimes blocked. The following rules summarize the conditions for allowing or disallowing multiple access to the same SAS file with any engine except the CONCUR engine:

If a file is open for input, another user may also open that file for input. The same process may also open the file for output, but all other access is denied.
If a file is opened for update, all other access is denied.
If a file is opened for output, the same process may also open the file for input if the file previously existed, but all other access is denied.

The one exception to these rules is when an OpenVMS search-string logical name is used as the physical path of a LIBNAME statement. In this case, when a SAS file is opened for input, another user may open that file for input. If the file is opened for update or output, all other access is denied, including access by the same process.

Under OpenVMS, the concurrency engine (CONCUR) allows concurrent read and write access to native data sets. For details, see Using the CONCUR Engine.

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