DB2 Server for VM: System Administration

Setting Up the CMS Communications Directory

You must define a CMS communications directory when one of the following is true:

• You access a remote application server through the VTAM product
• The resid and server name are not the same
• You use SECURITY=PGM
• The database name is longer than 8 bytes
• You access a database using TCP/IP.

The CMS communications directory provides SNA address resolution for the application servers. If this file does not exist or does not contain an entry, or if you issue the COMDIR OFF BOTH command, then the following assumptions are made: that the application server name is the same as the resid, the application server is within the same TSAF collection as the application requester, and SECURITY=SAME.

Any type of abend in the user machine (whether it is an application or initiated by the application requester code) can cause the CMS communications directory in virtual storage to be unloaded automatically. If there is a user-level directory, reload it by using the SET COMDIR RELOAD USER command. If there is a system-level directory, reload it by using the SET COMDIR RELOAD SYSTEM command.

Issue the QUERY COMDIR command: if the directory is unusable, this command returns an UNLOADED indicator. In this case, the communications directory is reloaded for you.

Note:

DB2 Server for VM makes use of the CMS NAMEFIND command when resolving CMS communications directory nicknames from database names. The NAMEFIND command should be issued within PROFILE EXEC or SYSPROF EXEC after the SET COMDIR command to prevent virtual storage fragmentation.

For more information on the CMS communications directory, see the VM/ESA: Connectivity Planning, Administration, and Operation manual. If you intend to access non-DB2 Server for VM application servers, also refer to the Distributed Relational Database Connectivity Guide manual.