Large-transfer writing, Large- transfer writing – HP NonStop G-Series User Manual
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Configuring Automatic Transaction Processing
HP NonStop AutoTMF Software User’s Guide—429952-014
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Large-Transfer Writing
Unstructured access to either unstructured files or structured files also permits large
transfers to be used if the appropriate BULK I/O interfaces are used.
When a file is audited, some the following rules apply to the use of unstructured
access:
•
A structured audited file cannot be opened for write access. An attempt to perform
such an open results in an error 80. TMF and the file system do not permit
unstructured updates to an audited structured file. TMF auditing is based on the
logical records of the file; unstructured access changes the physical structure of
the file, so the changes cannot be properly reflected in the TMF audit.
•
Unstructured read access to an audited file, structured or unstructured, is not
restricted.
•
Large transfer updates to unstructured audited files are now supported by the
NonStop OS. The emulation of large transfers is described below in
.
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