GDSX (Extended General Device Support) Manual

User Exit Descriptions

Extended General Device Support (GDSX) Manual—529931-001

9-2

DEVICE^HANDLER

This procedure is typically used to modify the communication of each thread between a

requester and another file (often a terminal). Running copies of DEVICE^HANDLER

code are called DEVICE^HANDLER tasks.

A DEVICE^HANDLER task is created by a call to the DEVICE^HANDLER procedure

as follows:

1. When TSCODE receives and processes an SCF START SU command, or when

the first open message is received by TSCODE for an SU, TSCODE opens the file

to which the SU is mapped.

2. The SU file is opened for nowait I/O (the OPEN flags parameter is set to a value

that is greater than or equal to 1).

3. TSCODE assigns the opened file a file number, an actual Guardian file number or

an ITC file number, and passes the file number when calling DEVICE^HANDLER.

Each request sent from a DEVICE^HANDLER task to a subdevice under a LINE does

not go directly to the subdevice. The I/O operation is sent first to the LINE^HANDLER

task associated with the subdevice. Nevertheless, the DEVICE^HANDLER task sends

I/O to the file number, just as it would if there were no LINE^HANDLER. TSCODE

handles the routing of the message to the LINE^HANDLER.

filenum input

INT:value

is the file number or ITC file number of the file that the DEVICE^HANDLER task is

to handle. The file is often a terminal. When this user exit is called, TSCODE has

already opened this file with the flags parameter of OPEN set to a value that is

greater than or equal to 1, and assigned filenum, which is the same as the actual

Guardian file number if the corresponding SU is not configured under a LINE.

internal-number input

INT:value

is the unique GDSX internal number for the file associated with this task. This

number may be used to identify the file in user-generated log messages, and may

also be used as an index into an array of pointers to the DCB table. (The DCB

may be used to access information about the file associated with this task.)

PROC DEVICE^HANDLER ( filenum !

,internal-number !

,terminal-type ); !