The SAS OLAP Server is a started task that sits in a wait state for MDX queries from an OLAP client application. Unlike a SAS Workspace Server session that is started at each submission of a SAS program and then terminated when the program completes execution, the SAS OLAP Server remains active until its SAS server session is stopped, restarted, or the physical machine that it is running on is restarted.

SAS data or third-party DBMS servers that are used in OLAP queries for drillthrough, aggregation, or ROLAP tables are initialized either when the SAS OLAP Server is started, or when they are referenced the first time. They are allocated via a SAS library assignment based on metadata information for the library definition. If one of these table servers is restarted, then the OLAP Server's connection to that server is broken and the library association is lost, which will result in disconnection errors generated by the OLAP Server.

For example, the following error was generated in the SAS OLAP Server log when a query to a ROLAP table was made against the OLAP Server following a restart of the Oracle server.

   ERROR: ORACLE prepare error: ORA-03135: connection lost contact.

   The server encountered an error accessing a source data table.

   ERROR: SQL passthru expression contained these errors: 
   ERROR: ORACLE prepare error: ORA-03114: not connected to ORACLE. 

Therefore, if a data server that is external to the OLAP Server session is restarted, you will need to restart the SAS OLAP Server in order to re-establish the connection with that server. This is necessary in order to allow future queries to the corresponding tables to execute correctly. The restart of the OLAP Server can be paired with any automatic restarts for your external DBMS servers.

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