SAS/SHARE User's Guide

Accessing SAS Files through a SAS/SHARE Server

SAS Data Library Access Provided by a SAS/SHARE Server introduces a SAS/SHARE server into the preceding diagram.

SAS Data Library Access Provided by a SAS/SHARE Server

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The SAS/SHARE server enables multiple clients to effectively share the same SAS file at the same time. In this context, share means to allow access by multiple clients to a different unit (for example, an observation) in the same SAS file. In the diagram, Client 1 can read from and write to observation 2, and Client 2 can read from and write to observation 3 in the same SAS file. Both clients can read the same observation at the same time. However, only one client at a time can write to an observation.

The server enables client access to the lowest unit of the SAS data library hierarchy through its powerful lock manager facility. Locks are applied in either of two ways:

A client may specify an explicit lock with a LOCK command or a LOCK statement.
A client operation may automatically submit a request for an implicit lock.

The SAS/SHARE server evaluates each incoming client request to access a particular SAS data library unit (for example, a data library, a data set, or an observation) against a complex set of locking rules whose application seems transparent to clients. The server balances the client requests for access to data while ensuring the integrity of that data. The server grants permission to a qualifying client and denies a conflicting request. The denied client receives an informational message. For more information about server locking rules, see Locking SAS Data Objects. For information about the use of the LOCK command and the LOCK statement, see Locking Objects Explicitly (LOCK Statement), and Locking Explicitly in a SAS Window (LOCK Command).

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