CONNECT

When an AOR with shared data table support issues a read request (or starts a browse sequence) for a remote file, CICS® attempts to establish a connection to a data table for that file. This operation is performed automatically, and is known as an SDT CONNECT.

If the FOR is registered as a shared data table server, CICS establishes a cross-memory link from the AOR to the FOR (subject to security checks) and calls the shared data table server to ask whether there is an available data table for the file. If there is, a connection is made between the AOR and the data table.

If the CONNECT is successful, cross-memory services are used, whenever possible, to access the file while the connection exists.

If the CONNECT fails, the file request is function shipped exactly as it would have been if shared data table support were not available. The action taken for subsequent remote file requests depends on the type of failure as described below.

If the CONNECT fails because of a permanent condition (such as CICS not being defined as an MVS subsystem), no further CONNECT attempts are made during the CICS run.

If the CONNECT fails because of a potentially transient condition that is not under the control of the file owner, another CONNECT attempt is made for the next suitable request after about ten minutes have elapsed. This type of condition includes:
  • Failing a security check
  • Failing to obtain storage
  • Failing to load a program
When a region's CONNECT requests are rejected because of a security check failure, the related security violation messages might be issued at 10-minute intervals.
If the CONNECT fails because of a potentially transient condition that is under the control of the file owner, another CONNECT attempt is made for the next suitable request following notification that at least one new file is available for shared access on the MVS system. This type of condition includes:
  • File owner is not logged on as a server
  • File is not associated with a data table
  • File is disabled, although associated with a data table
  • File is closed, although defined as a data table
After an AOR connects to a remote file successfully, it remains connected unless one of the following events occurs:
  • The AOR deletes its remote file definition

    In this event, the connection is broken immediately.

  • The FOR closes or disables the file

    In this event, the disconnection is scheduled at the next non-update request and is effected after all current browse sequences have terminated. See Disconnection.

If these events are later reversed, a valid connection is established in the same way as before.

Notification that a new file is available for shared access

When a data table is opened by an FOR, it becomes available for CONNECT attempts at the start of loading for a CICS-maintained data table, or at the completion of loading of a user-maintained data table. Other CICS regions are notified that a data table has become available. Notification is also made when a data table (or a file that uses a CICS-maintained data table) is enabled, having been previously disabled.