HP Integrity NonStop H-Series - Manual (Page 60)

Configuring Automatic Transaction Processing
HP NonStop AutoTMF Software User’s Guide—429952-013
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Large-Transfer Writing
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Large transfer updates to unstructured audited files are now supported by the
NonStop OS. The emulation of large transfers is described below in
Large-Transfer
Writing .
Some third-party programs perform unstructured read/write opens of a structured file.
Careful analysis of third-party programs has revealed that in most cases, these
programs did not attempt to update the file; read/write access was requested because
read/write access is the default.
If an error 80 occurs on an unstructured open of an audited structured file, NonStop
AutoTMF software will retry the open for read-only access. The retry allows some
programs to run successfully.
Programs that do attempt to update the audited structured file will receive an error 49
on the write operation. No known method can make such programs work with NonStop
AutoTMF software. If an error 49 occurs, either the file must be unaudited or the
program changed to use conventional record updates.
Large-Transfer Writing
Large transfer reads are permitted on audited files without a transaction, so these
reads are processed without emulation or automatic transactions.
Some applications use the file-system large-transfer facility to load large files quickly. If
the application issues a SETMODE 141 call, the application can then perform 56 KB
unstructured writes directly to the disk.
Until recently, such large-transfer write operations to an audited unstructured file were
not permitted by the file system. To emulate large-transfer writes, NonStop AutoTMF
software deblocked the large write into an equivalent number of 4KB writes. If the file
was opened in nowait mode, all writes except the last were waited. This emulation
offered a trade off between the efficiency of large transfers and the ability to audit and,
thereby, replicate such files.
However, recent versions of the file system (G06.20 and later) support large transfers
to audited unstructured files; if NonStop AutoTMF software is running on a system that
supports large transfers, it takes advantage of the feature to provide optimum
performance.
NonStop AutoTMF software cannot emulate unstructured writes (either with large or
small transfers) to audited structured files.
Transaction File (TFILE)
The TMF Application Programmers Guide describes the use of the TFILE ($TMP) to
manage multiple transactions in a multi-threaded program. Because NonStop
AutoTMF software also manages multiple transactions and transactions in parallel with
the program transactions, NonStop AutoTMF software opens the TFILE. For this
reason, the TFILE must be managed as a shared resource, even though the TFILE
appears to the program as a dedicated resource.