Occasionally, you might need to establish or break a connection between the master catalog and a user catalog, or between BCSs and VVDSs. For example, the DIAGNOSE command issues a message if a BCS and VVDS are connected, but there are no data sets on the VVDS's volume that are cataloged in the connected BCS. If this is the expected condition, breaking the connection between the VVDS and the BCS eliminates unwanted messages from DIAGNOSE.

See Figure 1 for an illustration of how master and user catalogs, and VVDSs, are connected.

A BCS is connected to the master catalog of each system that shares the catalog. However, when the BCS is defined, it is only connected to the master catalog on the same system. To connect the catalog to other sharing systems, use the IMPORT CONNECT command. A catalog does not have to exist in order to connect it to a master catalog.

If you specify ALIAS on the IMPORT CONNECT command, any aliases that are already defined in the target master catalog for the catalog are maintained. Aliases that are not already defined in the target master catalog are not added, however. ALIAS can be specified even if no aliases are defined for the catalog.

Alternatively, you might need to disconnect a catalog from a system. In this case, use EXPORT DISCONNECT. This command removes the catalog's entry from the master catalog, and deletes all associated aliases. You do not have to lock a catalog before disconnecting it. Any jobs oriented to the catalog should end normally.

The catalog does not have to exist in order to disconnect it. For instance, if another system has deleted the catalog, any sharing system can disconnect that catalog.

You cannot use DELETE NOSCRATCH to delete a catalog's entry in the master catalog.

The system connects VVDSs with BCSs as the need arises. However, if you want to explicitly establish a connection between a VVDS and a BCS, you can use DEFINE RECATALOG, specifying the VVDS as the entry name, and specifying the BCS in the CATALOG parameter.

To break the connection between a BCS and a VVDS, use DELETE NOSCRATCH, specifying the VVDS as the entry name, and the BCS in the CATALOG parameter. If the VVDS is available, it is checked to determine if the BCS in the CATALOG parameter has any data sets on the volume. If data sets are found on the volume, the DELETE command will fail. If the VVDS is not available, no check is performed.