Guardian Procedure Calls Reference Manual (G06.25+)

Guardian Procedure Calls (W-Z)
Guardian Procedure Calls Reference Manual—522629-013
16-10
WRITE[X] Procedures
For relative and entry-sequenced files, the current position is that of the record
just inserted and the current primary-key value is set to the value of the
record’s primary key.
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Duplicate record found on insertion request
When attempting to insert a record into a key-sequenced file, if a duplicate
record is found, the WRITE[X] procedure returns error 10 (record already
exists) or error 71 (duplicate record). If the operation is part of a TMF
transaction, the record is locked for the duration of the transaction.
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Unstructured files
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DP2 BUFFERSIZE rules
DP2 unstructured files are transparently blocked using one of the four valid
DP2 blocksizes (512, 1024, 2048, or 4096 bytes; 4096 is the default). This
transparent blocksize, known as BUFFERSIZE, is the transfer size used
against an unstructured file. While BUFFERSIZE does not change the
maximum unstructured transfer (4096 bytes), multiple I/Os may be performed
to satisfy a user request depending on the BUFFERSIZE chosen. For
example, if BUFFERSIZE is 512 bytes, and a request is made to write 4096
bytes, at least eight transfers, each 512 bytes long, will be made. More than
eight transfers happen, in this case, if the requested transfer does not start on
a BUFFERSIZE boundary.
DP2 performance with unstructured files is best when requested transfers
begin on BUFFERSIZE boundaries and are integral multiples of BUFFERSIZE.
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If the WRITE[X] is to an unstructured disk file, data is transferred to the record
location specified by the next-record pointer. The next-record pointer is
updated to point to the record following the record written.
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The number of bytes written
If an unstructured file is created with the odd unstructured attribute (also known
as ODDUNSTR) set, the number of bytes written is exactly the number
specified in
write-count. If the odd unstructured attribute is not set when
the file is created, the value of
write-count is rounded up to an even value
before the WRITE[X] is executed.
You set the odd unstructured attribute with the FILE_CREATE_,
FILE_CREATELIST_, or CREATE procedure, or with the File Utility Program
(FUP) SET and CREATE commands.
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File pointers after WRITE[X]
After a successful WRITE[X] to an unstructured file, the file pointers have these
values:
current-record pointer := next-record pointer; next-record pointer := next-record
pointer +
count written; end-of-file (EOF) pointer := max (EOF pointer,
next-record pointer);