gtpd2m0kData Communications Services Reference

Data Areas and Input/Output

Keypoint Record C

Keypoint record (CK8KE) contains system information required by the IPL and restart sequences to bring the system to 1052 state. It is a core resident keypoint which is shared by all processors in a loosely coupled complex.

The information in CTKC which is pertinent to CRAS support includes the CRAS status table (CR0AT), the initial status of each processor's first two entries of the line status table, and in the case of 3270 native console support, the MORE... timeout value and a table of subchannel addresses to be used as alternate consoles in the event of failure on a system console. All of this information is generated via the SIP CRASTB macro (for more information about the SIP CRASTB macro, see TPF System Generation). The CRAS table is the only portion of this information that may be modified during online operation (see ZACRS--Alter CRAS Table). All other portions remain unchanged throughout the life of the system.

CRAS Status Table

The CRAS table (CR0AT) is the focal point for TPF's CRAS support. All information required to support an installation's current CRAS configuration is maintained in this table. The CRAS configuration is dynamic; it may be modified via command during online operation as dictated by varying levels of system activity. It will also be modified by the console fallback routines whenever a hardware failure forces an automatic switch of a system console.

The initial CRAS configuration is defined by the user at system generation time via the CRASTB macro in the system initialization package (SIP). The hardware locations (subchannels) of the Prime CRAS, the RO, and all alternate consoles (for fallback) are specified at this time for each processor in the loosely coupled (L/C) complex. SIP uses this information to build the initial CRAS table in keypoint record (CK8KE). The CRAS table remains unchanged across an IPL.

Certain privileged and system oriented messages are restricted to CRAS devices. The CRAS table is used to control entry of these messages into the system; privileged messages entered by non-CRAS devices will be rejected. Input is accepted from all CRAS devices when the system is in or above CRAS state. Below CRAS state, input is accepted only from 1052/3215 and locally attached 3270 CRAS devices.

Only the Prime CRAS and RO CRAS need be dedicated CRAS terminals. Alternate CRAS devices may be used for application requirements. If a fallback condition selects as Prime CRAS or RO CRAS an alternate CRAS terminal currently being used by an application, the system will automatically log the device out of the application and log it into the system message processor (03-CSMP).

Line Status Table

The line status table contains the current status of the communication network attached to the multiplexor channel via 2703/3705 EP and locally attached 3270 devices. It is primarily used by the CRAS package to determine the physical device addresses to be used for the system consoles, and whether or not a device is eligible for fallback. To ensure that the system successfully reaches 1052 state, upon every IPL the PRC and RO entries of the LSTB are overlayed with the initial LSTB data (SIP created) from CTKC.

Command Editor Tables

The command editor tables are program and fixed file records that essentially control command input and output; see 03-CSMP for additional information. These tables define each command's input characteristics and indicate which FSC(s) are to receive a copy of the response. See Input Message Restrictions for further details. Modification of these tables is via source update. For more information, see Modifying the Command Editor Tables or the ZFMSG command in TPF Operations.