Changing the Link3270 bridge request SYSID

The initial values of the SYSID and netname of the default CICS® region to which the request is to be routed are derived from the value of the REMOTESYSTEM option of the installed user program definition. If REMOTESYSTEM is not specified, or there is no program definition, the sysid and netname passed are those of the local CICS region.

The region to which the request is routed is determined as follows:
  • The NETNAME and the SYSID are not changed.

    CICS tries to route to the SYSID as originally specified in the communications area.

  • The NETNAME is not changed, but the SYSID is changed.

    CICS updates the communications area with the NETNAME corresponding to the new SYSID, and tries to route the request to the new SYSID.

  • The NETNAME is changed, but the SYSID is not changed.

    CICS updates the communications area with a SYSID corresponding to the new NETNAME, and tries to route the request to the new SYSID.

  • The NETNAME is changed and the SYSID is changed.

    CICS overwrites the communications area with a SYSID corresponding to the new NETNAME, and tries to route the request to that new SYSID.

If the NETNAME specified is invalid, or cannot be found, SYSIDERR is returned to the dynamic routing program, which may deal with the error by returning a different SYSID or NETNAME. See Handling route selection errors of Link3270 bridge requests.

When you return control to CICS with return code zero, CICS first compares the returned SYSID with its own local SYSID:
  • If the SYSIDs are the same (or the returned SYSID is blank) CICS executes the link request locally.
  • If the two SYSIDs are not the same, CICS routes the request to the remote CICS region, using the returned transaction name.