ICL 1900 Series George 3 Operating System Commands

ACCESS (AC)

Function

Enables a program, such as a High Level Scheduler, to read from, or write to areas within GEORGE, by means of the file handler, file reader, file writer, EDS and WMC PERI extracodes.

Format

ACCESS peripheral,type,unit number

where:-

peripheral must be one of *DAn, *FHn, *FRn, *FWn or *PBn.

type refers to a named type of information used by built-in GEORGE routines.

unit number is only applicable to the COMMS channel. It must be expressed in the form Unumber and refers to the unit number of the required virtual 7900.

Acceptable information types and the peripheral names that may be used to access them are given in the following table.

Notes

1. *ED and *FD are permitted in place of *DA in the current mark
2. The HLSACTIVE channel provides all the facilities that are available on the other ACCESS channels except COMMS
3. The HLSPASSIVE channel provides all the passive facilities (that is all except the SCHEDCONTROL PERI extracodes, and the HLSTEMPQ PERI extracode that removes a block from the HLSTEMPQ).
4. The COMMS (WMC) channel is for private use by Communications Manager (CM) under GEORGE 3 only

Forbidden contexts

NO CORE IMAGE

Execution

If a permitted combination of peripheral name and information type name is specified, an off-line peripheral activity is set up to control transfers of the specified type of information between GEORGE and the subject program.

Notes

1. If the peripheral name specified is that of a peripheral already in use by the program, it is released, and a new activity is set up.
2. The extracodes will normally be used by subroutines that are described with the other HLS PLAN subroutines.
3. Only users or jobs with the privilege HLSEXT may use this command. HLSEXT is normally a non-permanent privilege available to system issued jobs, jobs going through built-out log analysis or jobs running under one of the users :MANAGER, :SYSTEM or :JOURNAL. The installation manager may, however, still create a privilege with this name by using NAMEPRIV.
4. Only system issued jobs may use the HLSACTIVE, HLSTEMPQ and SCHEDCONTROL facilities.
5. For Communications Manager:-
   
   The command is errored with the message
   
       PERIPHERAL z NOT ALLOWED
   if virtual 7900s are not supported by GEORGE or
       UNIT IS ALREADY ALLOCATED
   if the virtual 7900 is being accessed by a different job, or if the virtual 7900 is already initialised, the is, the supervisory segment INITIALISE has been sent. In this situation the operator must MOP it OFF first.
   Note: Virtual 7900s are not applicable to and cannot be accessed by GEORGE 4.
   The COMMS channels are disestablished when the virtual 7900 is MOPped OFF and established when it is MOPped ON and are always processed in the order in which they were set up. The COMMS channels are not affected by the restore time macros IPCPRIV and IPCREOFF.
   The CM user must hold the privilege HLSEXT before being allowed to ACCESS COMMS channels. There is no requirement for the CM program using the COMMS channels to be REALTIME. However, as with standard WMC links certain actions (for example program displays or program issued commands) are delayed until the WMC transfers are terminated.
   WMC ENQUIRY modes are not supported and WMC OPEN, CLOSE and CANCEL modes are never given a rejected response.
   The size of WMC read transfers in Communications Manager must be equal to the size of the output buffer. The size of WMC write transfers in Communications Manager must be in the range 3 to the size of the input buffer in GEORGE. The buffer size is specified in the INITIALISE command sent by GEORGE and is currently 67 eords.
   To help approximate a RIM (see Chapter 6 of Communications Manager (TP4420)) interface the following differences between GEORGE's dialogue with a virtual 7900 and a real 7900 should be noted:
   
   • The INITIALISE supervisory segment specifies the program name GEO3 in word 2
   • The end of restart section bit (bit 6) in data segments headers is copied to the end of NPU bit (bit 1)

Error Messages

PERIPHERAL z NOT ALLOWED
z IMPERMISSIBLE
PERIPHERAL PARAMETER MISSING
2ND PARAMETER MISSING
THIS COMMAND IS NOT FOR GENERAL USE
UNIT z ALREADY ALLOCATED
UNIT z IS NOT A SUITABLE DEVICE