- Entry from:
- VTAM®
- Entry point:
- routine name
Contents of registers at entry: - Register 0:
- Length of logon message
- Register 1:
- Address of first byte of logon message. For LOGON requests, VTAM searches the interpret table
again, after USS translation, looking only for the specified APPLID.
After USS translation, register 1 contains the address of the first
byte of the APPLID.
- Register 2:
- Address of an 8-byte logical unit name
- Register 4:
- Address of parameter list for the network identifier and resource
name.
- Register 13:
- Address of a 72-byte save area provided by VTAM
- Register 14:
- Return address
- Register 15:
- Address of entry point of this routine
Operation: The logon-interpret routine is run synchronously
in pageable storage under the control of VTAM and not under the control of an application
program. For the application program to receive the logon, this routine
must validate the logon, obtain the name of the application program
to receive control, and provide this name to VTAM. Otherwise, the routine specifies that
the logon is not valid or that the name of the application program
was not found.
The logon-interpret routine must also:
- Save and restore the contents of registers 2–14 when receiving
and passing control
- Use re-enterable code (the routine must not store anything within
itself or modify itself during execution)
- Perform no I/O operations; an I/O request causes the routine to
terminate abnormally.
Because the logon-interpret routine operates at VTAM's main task dispatching priority,
there is a possibility of lockout if a wait requires another task
action. The routine gets control in supervisor state with a VTAM storage key, so errors within
the routine could cause damage to VTAM or
to system control blocks and modules.
Note: - You can modify the logon message that is passed to the interpret
routine. However, remember these two points:
- VTAM does not look at the
changed storage; it is passed as user data to the application.
- You should modify with caution, as modification outside the message
storage boundaries could result in VTAM outages.
- All data is addressable only in 24-bit mode.
Contents of registers at exit: Registers 0 and
1 contain the name of the application program (in EBCDIC characters)
with which the logical unit is to establish a session:
- Register 0:
- First 4 characters of name (left-aligned).
- Register 1:
- Last 4 characters of name (left-aligned).
- Registers 2–14:
- Restored to condition at entry.
- Register 15:
- Return code:
- 00
- Application program was found and the name is placed in registers
0 and 1.
- Nonzero
- Application program was not found and the name is not placed in
registers 0 and 1.
If the name of the application program contains fewer
than 8 characters, use blanks to provide a name with 8 characters.