Pathway/iTS System Management Manual (G06.24+)

Setting TMF Parameters
HP NonStop Pathway/iTS System Management Manual—426748-002
E-4
Timeouts on SEND Operations to Servers
Depending on the type of file access attempted, the TCP either allows the SEND
statement to execute or issues the appropriate error message.
In a PATHMON environment that normally runs with the TMF subsystem, do not use
the following commands to turn off TMF subsystem operations temporarily:
SET TERM TMF OFF
SET PROGRAM TMF OFF
The condition resulting from these commands appears to allow normal operation,
because the BEGIN-TRANSACTION statement that would have failed if the TMF
subsystem were stopped now appears to work; the TCP allows a SEND operation to a
server that can access and update only nonaudited files. Files updated by servers are
not protected by the TMF subsystem, and the TCP does not perform checkpoints
before or after SEND statements.
Timeouts on SEND Operations to Servers
Although the syntax of the SCREEN COBOL SEND statement does not include a
TIMEOUT clause, you can effectively supply one with the PATHCOM SET SERVER
command. When you include a TIMEOUT clause in the SET SERVER command, all
SENDs to that server class are timed by the TCP. If the specified number of seconds
elapses after a SEND operation is initiated and before a reply is received, the TCP
issues a Guardian operating environment CANCEL procedure call against the
outstanding I/O to the server. If the SEND operation was performed while the requester
program was in transaction mode, the transaction is automatically aborted by the file-
system. In such a case, the requester program discovers that the transaction was
aborted when it subsequently attempts to update the database (with another SEND
statement) or issues an END-TRANSACTION statement.
TCP Checkpointing Strategy
For PATHMON environments with the TMF subsystem running, the TCP uses the
following checkpointing strategy:
•
At the BEGIN-TRANSACTION statement, a full copy of the task’s context is made
to a secondary area (slot 1) in the extended data segment, and a checkpoint to the
backup is performed.
•
At the END-TRANSACTION statement, a full-context checkpoint is performed.
•
At the SEND statement with the SET SERVER TMF parameter defined as OFF, a
checkpoint is performed before and after the SEND statement when the SCREEN
COBOL program is outside of transaction mode. (Any time a SEND operation is
performed outside of a transaction boundary and the server attempts to lock or
update a record in an audited file, the operation fails with a Guardian error 75.)
•
At the SEND statement with the SET SERVER TMF parameter defined as ON, no
checkpoints are performed, whether or not the SCREEN COBOL program is in
transaction mode. This means that SEND requests to TMF protected servers that