AutoTMF Software User's Guide (Update 14)

Configuring Automatic Transaction Processing

HP NonStop AutoTMF Software User’s Guide—429952-016

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Considerations

As mentioned above, record-level transactions increase transactional activity and

processing complexity, and they are useful only in very specific situations. Users

should configure record-level transactions when a careful analysis of a program’s

locking behavior leaves no other option or after being instructed to do so by product

support.

Changing Nowait IO to Waited IO

To commit automatic transactions, AutoTMF must find a point where no records are

locked by the application program. Most programs have such points, but others have

complex algorithms that lock records on some files before unlocking records on other

files, leaving no commit opportunity. The configuration options SEPARATETX and,

rarely, RECORDTX can be used in most cases to provide the necessary commit

points.

However, a program may still be too complex to be managed using these methods.

The WAITEDIO feature handles these rare cases, where a program opens a file

multiple times for NOWAIT processing, and performs concurrent I/O to the same file. If

the I/Os are performed under a common transaction, an I/O may be in progress at all

times, preventing the transaction from being committed. If the I/Os are performed

under separate transactions, operations that need to lock the same record on different

opens may cause an internal deadlock.

If the WAITEDIO option is enabled for a NOWAIT file open, AutoTMF performs the

following operations:



Issues an AWAITIO immediately after the read, write, or update operation.



Following the AWAITIO, AutoTMF commits any outstanding transaction using its

usual algorithms, as directed by the configuration.



Saves the values returned by AWAITIO, and returns control to the program as if

the READ or WRITE operation were still in progress. After a READ, the data buffer

contains the input data.

FILEINFO and FILE_GETINFO_ return the error code for the last READ or WRITE

operation (instead of AWAITIO). Any error returned by the AutoTMF generated

AWAITIO is not visible to the application until the application calls AWAITIO. When the

program calls AWAITIO, AutoTMF returns the saved values and makes the operation

error visible to the application.

Configuration

To enable waited I/O, configure both the ATMFFILESET and ATMFPROGRAM

WAITEDIO attributes. A program configured using the WAITEDIO option uses Waited

I/O only for audited files that are also configured for Waited I/O.