LINKTABL

A link table (LINKTABL) entry describes any RSCS connection to a peer node, printer, or workstation created by a LINKDEFINE statement or by the DEFINE and START commands. Each link defined to the RSCS virtual machine has a LINKTABL entry. The TLINKS field in the CVT points to the chain of LINKTABL entries. The first LINKTABL entry in the chain contains information about the local RSCS node. The LINKID field in this LINKTABL contains the node ID of the local node.

Most LINKTABL fields correspond to the operands of the LINKDEFINE statement and the DEFINE or START commands. Fields that represent operands of the LINKDEFINE statement and START and DEFINE commands have two forms:

LACTxxxx fields for the active, or current, value of a field
LDEFxxxx fields for the default values specified on a LINKDEFINE statement or on the DEFINE command.

The LACTxxxx fields contain copies of the values in the LDEFxxxx fields when the link is inactive. If the link is started by a START command that specified PARM or OPARM values, only the values in the LACTxxxx fields are changed; they are restored when the link becomes idle.

All PARM, OPARM, or UPARM parameters are represented by a pointer in the LINKTABL. This field points to a data area that contains a half-word header, indicating the number of characters in the parameter string, and the text of the string. If no parameters are specified on the link, this pointer contains zeros.

The LINKTABL contains LFLAG fields indicating the link’s status. It also contains ECBs and queue anchors for commands and work queues for active links. The LINKTABL anchors and keeps counts for TASHADOW queues that represent inactive files on the link. Other LINKTABL fields govern multistreaming, link message subscriptions, SNA and TCP/IP sessions, and the node and user ID of the START command originator. The LINKTABL also contains a pointer to the ITRACE settings used for the link task. For more information about the LINKTABL format, see LINKTABL.

When a link is deleted, its LINKTABL entry remains in the LINKTABL chain and its LINKID field is cleared. When a new link is defined, RSCS searches the LINKTABL chain to find a LINKTABL entry containing an blank LINKID field. If it finds one, RSCS uses the existing structure to create the LINKTABL entry for the new link. If no links have been deleted (there are no cleared LINKID fields), RSCS creates a new LINKTABL entry for the new link.

When RSCS initializes, all LINKTABL entries are added to a hash table based on their link ID. Tasks call DMTCOMLK to locate LINKTABL entries in the hash table (see DMTCOMLK and DMTCOMGG for more information on DMTCOMLK).