TMF Application Programmer's Guide (G06.26+)

TMF Programming Environment
HP NonStop TMF Application Programmer’s Guide—522419-005
1-7
The Current Transaction
Summary of Requester Actions
In general, TMF requester processes do the following:
•
Open any necessary server processes.
•
Initiate TMF transactions.
•
Format work requests describing the necessary database manipulations and send
them to the appropriate servers by way of the message system.
•
Receive reply messages from the servers, indicating success or failure.
•
Terminate transactions.
Summary of Server Actions
In general, TMF server processes do the following:
•
Accept request messages from requesters by way of $RECEIVE.
•
Obtain any necessary file or record locks.
•
Once acquired, the locks on any records or rows that have been updated, inserted,
or deleted are automatically maintained by the disk process until the transaction is
either committed or aborted and backed out.
•
Execute I/O statements to perform the requested actions against the database.
•
Determine the success or failure of each I/O operation by way of the associated
completion code or file system error code.
•
Format reply messages and send them to the appropriate requesters.
The Current Transaction
An important concept within the TMF programming environment is that of the current
transaction. The current transaction is an implicit identifier that specifies the particular
transaction on behalf of which a process can perform operations on files being audited
by the TMF subsystem.
At any given time, the current transaction for a requester or server is either of the
following:
•
A nil value, indicating that there currently is no transaction in progress
•
The transaction identifier of the particular transaction on which the requester or
server is currently working