Using SORDER to control network search order

SORDER controls the order in which the APPN and subarea portions of the network are searched when adjacent SSCP routing is performed for a search request received by an interchange node or migration data host. SORDER can be specified as a start option or coded on individual ADJSSCP table definitions (or both). In general, the SORDER start option value should be chosen based on where the most frequently sought after resources are located (in the APPN network or in the subarea network). Although this approach provides the best search performance for MOST resources in the network, a single SORDER value rarely results in optimal search performance for ALL resources. For these cases, the search order can be specified on a more granular level by coding SORDER individually on each ADJSSCP table.

The default value for the SORDER start option (SORDER=APPN) will cause VTAM® to prefer searching the APPN network before searching the subarea network (adjacent CDRMs). However, if the CDRM that owns the target resource is known (defined on the cross-domain resource definition or learned from previous searches), new searches will be sent to this CDRM first, before searching the APPN network. If the APPN network should always be searched first even before the owning CDRM (for example, to maximize the use of High Performance Routing), SORDER=APPNFRST should be used.

If most target resources are still located in the subarea portion of the network, SORDER=SUBAREA should be used. In this case, the APPN network will be searched only after all adjacent CDRMs have been searched. If VTAM has been enabled for APPN but there are currently no resources located in the APPN network (that is, no APPN searching should be performed), SORDER=ADJSSCP should be used. With SORDER=ADJSSCP, the APPN network is only searched if an ISTAPNCP ADJCDRM entry has been explicitly coded in the ADJSSCP table that is chosen for the search.

To specify the search order for individual adjacent SSCP tables, code the SORDER operand on the NETWORK or CDRM statements that define each adjacent SSCP table. If SORDER is coded on a NETWORK statement, that value will sift down to all subordinate adjacent SSCP tables until the next NETWORK (or ADJLIST) statement is encountered. To override the SORDER value on the preceding NETWORK statement, code the SORDER operand on the CDRM statement that defines the subordinate adjacent SSCP table. To override the SORDER value on the preceding NETWORK statement with the current SORDER start option value, code SORDER=STARTOPT on the CDRM statement. (SORDER=STARTOPT is the default value for NETWORK statements.)

Notes:

If a search request is received by VTAM from the APPN network, SORDER is ignored. The search order used for searches received from the APPN network will depend on what information (if any) exists in the Directory Services database. The DISPLAY DIRECTRY command can be used to display information in the Directory Services database.
If SSCPORD=PRIORITY is specified and previous searches for the target resource have been performed, the search order can be modified based on the results of these previous searches. Use the DISPLAY ADJSSCPS command with the CDRSC operand to display the search order that will be used by VTAM on the next search for this resource.
If SORDER=APPNFRST, APPN or SUBAREA is specified for an adjacent SSCP table, any ISTAPNCP ADJCDRM entries coded within that table are ignored, because VTAM will automatically place the ISTAPNCP ADJCDRM entry in the appropriate position in the table. This is true regardless of where the SORDER value was obtained.
If SORDER=ADJSSCP is specified for an adjacent SSCP table and an ISTAPNCP ADJCDRM entry is not coded within that table, the APPN network will not be searched (unless SSCPORD=PRIORITY is specified and a previous search for this resource determined that it could be found in the APPN network).