Delayed activation of logical lines

This function enables you to perform an orderly activation of a physical resource and its associated logical resources. Because there is a hierarchical relationship between the physical resources (line and physical unit) and the logical lines, you can use this function to implicitly activate a logical line when the physical resources are explicitly activated.

The function creates a hierarchy between a logical line in a group (within an NCP major node) that has a PHYSRSC operand coded and the physical resource indicated by the PHYSRSC operand. This includes:

NCP/Token Ring interconnection (NTRI) physical resources (line and physical unit) and logical lines for INN link stations
NCP Packet Switched Interface (NPSI) physical resources (line and physical unit) and logical lines
Frame-relay physical resources (line and physical unit) and logical lines

If the OWNER operand is specified for both the physical unit and the logical line, the logical line is subordinate to the physical unit only when the owner of the physical unit is an owner of the logical line and the PHYSRSC operand is coded for the logical line group. Remember that a physical unit can have only one owner, but a nonswitched logical line can have multiple owners. If the OWNER operand is not coded for both the higher-level physical unit and the logical line, the logical line is always hierarchically subordinate to the physical unit, if this VTAM® can be the owner of both resources. See the z/OS Communications Server: SNA Resource Definition Reference for information about the OWNER operand.

Because only one VTAM can own the physical unit, yet the physical unit can be built into the hierarchy in multiple VTAMs (unless the OWNER operand is specified), only one VTAM can have the physical unit active and have logical lines subordinate to the physical unit. When explicit owners are not specified, if another VTAM owns a higher-level physical unit and the physical unit is activated by a second VTAM, the activation request issued by the second VTAM is rejected by the NCP. In this case, the second VTAM removes the higher-level physical unit from the hierarchy of all its subordinate logical lines. In this way, the logical lines within the second VTAM can still be activated by a mechanism other than being subordinate to the physical unit. After the hierarchy is broken in this way, it is not reconstructed even if this VTAM successfully reactivates the physical unit at a later time.

When the higher-level physical unit is a switched resource, not only is the physical unit limited to one owning VTAM, but the switched line can only have one owning VTAM as well. If a second VTAM attempts to activate the physical line, the activation request is rejected by the NCP. In this case, the second VTAM removes the higher-level physical PU from the hierarchy of all its subordinate logical lines.

For a switched physical line with a logical hierarchy, DWACT can be used in the switched major node definition or on the VARY ACT command issued for a switched major node. DWACT specifies whether to dial the switched PU when it is activated. This lets you avoid issuing a VARY DIAL command. DWACT can apply to both the switched physical PU and to one or more logical PUs in the logical hierarchy . Because the activation of the switched logicals cannot take place until the activation of the switched physical PU is complete, using DWACT can result in an activation failure for the switched logicals. For example, if the switched physical PU and the associated switched logical PUs are in the same switched major node, a VARY ACT of the switched major node with DWACT=YES results in a DIAL for the physical PU, but a DIAL failure for the associated logicals. However, a second VARY ACT of the switched major node with DWACT=YES results in activation of the associated switched logicals.

If there is a switched physical with a logical hierarchy, one of the following actions is recommended:

Define the switched physical PU and the associated switched logical PUs in the separate switched major nodes, then activate the switched major node with the physical PU before activating the switched major node with the associated logical PUs. DWACT can be specified in the switched major nodes or on the VARY ACT command of the switched major nodes.
Define both the switched physical PU and the associated switched logical PUs in the same switched major node, then activate the switched major node twice. To avoid error messages, DWACT can be specified on the physical PU in the switched major node (but not on the logical PUs in the switched major node). Then, issue a VARY ACT, DWACT=NO to activate the physical PU. Then issue a VARY ACT,DWACT=YES to activate the associated logical PUs.

For most multiple-domain environments, the OWNER operand should be specified for both the physical unit and the logical lines so that the owner of the physical unit and the set of subordinate resources is predetermined and does not vary. The OWNER operand provides a way to control activation while also providing a backup owner for the physical resource. This relationship remains even if there is a takeover of the NCP. For example, if the VTAM that owns the physical unit (and possibly some logical lines) releases the NCP and another VTAM acquires the physical unit, the physical unit is placed hierarchically above any logical line acquired from the other VTAM.

Activating logical lines hierarchically: Activation processing in a multiple-domain environment is the same as in a single-domain environment except for the difference in hierarchical relationships that could exist because of the checking of the OWNER operand. When a logical line is subordinate to a physical unit, the physical unit must be activated before the logical line is activated. When the physical unit is owned by another VTAM, but this VTAM is to own a logical line subordinate to the physical unit, the activation of the physical unit must be attempted so that this VTAM can see that the physical unit is owned by another VTAM. Note that a logical line that specifies a different OWNER from its associated physical resource is not hierarchically subordinate to that physical unit. In this case, the activation of the physical unit need not be attempted before the logical line can be activated.
Deactivating logical lines hierarchically: Deactivation processing in a multiple-domain environment is the same as in a single-domain environment except for the difference in hierarchical relationships that could exist because of the checking of the OWNER operand. In addition, hierarchical relationships could be affected by the rejection of a activation request sent by a VTAM to a higher-level physical unit that is owned by another VTAM.