Dynamic reconfiguration of frame-relay resources

Frame-relay PUs, which are type 1 PUs, are used in FRSESET (frame-relay switching equipment set) definition statements to create routing paths within an NCP. Each FRSESET definition statement can contain two to four frame-relay PUs, which define the primary routing partners and their optional backups. In the following example, PU A and PU B are the primary partners, while PU C and PU D are the backups. PU C is the backup for PU A, and PU D is the backup for PU B.

          frse3a3 FRSESET  SUBPORTS=(A,B,C,D)

If one of the primary partners is deactivated, routing can continue between the backup for the inactive primary PU and the remaining primary PU. Backup to backup routing is not permitted.

The VARY DRDS, MODIFY DR, and VARY ACT,UPDATE=ADD|ALL commands can be used to dynamically reconfigure frame-relay PUs and FRSESET definition statements. To delete a PU from a FRSESET, use VARY DRDS, MODIFY DR, or VARY ACT,UPDATE=ALL. To add a PU to a FRSESET, use VARY ACT,UPDATE=ADD|ALL. You cannot move frame-relay PUs, but you can delete a PU and add it back in the required position to accomplish a move.

The following rules apply when using dynamic reconfiguration for frame-relay resources:

Each FRSESET definition statement must have a domain-unique name.
The LMI (local management interface) PU must be statically defined as the first PU under a frame-relay line. The LMI PU cannot be used in a FRSESET and cannot be added (or deleted) dynamically.
Each PU in a FRSESET must be on a different frame-relay line.
A PU cannot be concurrently defined in multiple FRSESET definition statements.
Use UPDATE=ALL for initial activation. If VTAMLST is modified before initial activation, using UPDATE=IMPLICIT can cause NCP and VTAM® to have inconsistent definitions. If this occurs, issue a VARY ACT,UPDATE=ALL command to correct the problem.
To modify a statically defined FRSESET, all PUs in the FRSESET must first be deleted.
Note: Statically defined PUs that are deleted and then added back (for example, when adding backups to a statically defined FRSESET) are regarded as dynamic PUs.
A FRSESET cannot contain both static and dynamic PUs.
To delete a PU from a FRSESET, you must first deactivate the PU. Otherwise, the deletion fails and the PU is still present.
Do not delete either of the primary PUs from a dynamically defined FRSESET. Otherwise, remaining PUs in the FRSESET may be deactivated, and the FRSESET cannot be used until a primary PU is added.
PUs must be deleted from the frame-relay line and the FRSESET simultaneously.
When adding PUs to a FRSESET, PUs must be added to the frame-relay line and the FRSESET simultaneously.

If you do not follow these rules, you might receive messages IST322I, IST323I, and IST1350I. Do the following to correct the problem:

If the FRSESET was statically defined, delete all PUs and the FRSESET, correct the error, and then add back the PUs and the FRSESET.
If the FRSESET was dynamically defined, only the PU or FRSESET in error must be corrected.

If any PU in a dynamic FRSESET is deactivated, all other active or contact pending PUs in the FRSESET that have no potential routing partner become inoperative. The inoperative PUs go through recovery processing and are again active, although not currently usable for routing because they have no partner.

Data traffic flowing over the deactivated PU could be momentarily halted while the switch to the backup PU is performed. If the backup is not available, data traffic ceases. Data traffic also ends if the other primary PU is not available; backup-to-backup routing is not permitted.

If the data is routed through a backup PU and the primary PU becomes available, routing automatically switches back to the primary PU.