Guardian Procedure Calls Reference Manual

compared to the same file managed by SIO before D20. The file is not actually larger, as the
same amount of disk space is allocated in both cases. The difference is that in the newer
version, the last part of each new extent is immediately put into use.
• SIO always performs buffered I/O, using the disk process buffering mechanism to enhance
performance, when writing to an EDIT file. You can force SIO to flush buffered data to disk
by calling WRITE^FILE and specifying a write-count of -1.
• For performance reasons, it is recommended that you provide a block buffer with a length of
about 2100 bytes. This is because SIO normally requires slightly more than 2048 bytes to
assemble EDIT file pages.
• You must specify either read or write access when opening an EDIT file; read/write access is
not permitted.
Level-3 Spooling Considerations
• Level-3 spooling allows multiple records to be sent per message to a spooler collector, greatly
reducing the number of messages required to do spooling. To use level-3 spooling with SIO,
you must open a spooler collector by calling OPEN^FILE. These requirements must be met:
◦ You must set the LEVEL3^SPOOL^ENABLE flag ON in the call to OPEN^FILE.
◦ You must provide a block buffer with a length of at least 1024 bytes.
◦ The open exclusion mode of the file must be shared.
◦ The maximum record length of the print line buffer is 900 bytes.
If any of these requirements are not met, level-3 spooling is not enabled. You can verify whether
level-3 spooling is enabled by calling the CHECK^FILE procedure and specifying the
FILE^LEVEL3^SPOOLING operation.
• CONTROL or SETMODE operations are not allowed on a file that is opened by SIO for level-3
spooling; error 2 is returned by CONTROL or SETMODE for any operation. Certain CONTROL
operations can be requested in a call to OPEN^FILE or WRITE^FILE; these continue to be
available when a file is opened for level-3 spooling.
• The spooler interface procedures, through which SIO performs spooling, do not support nowait
I/O. You can set the NOWAIT flag ON in a call to OPEN^FILE and WRITE^FILE, but SIO still
performs I/O operations to a spooler collector in a waited manner.
Example
ERROR := OPEN^FILE ( COMMON^FCB , IN^FILE , BUFFER
, BUFFER^SIZE , FLAGS , FLAGS^MASK , , PROMPT );
Related Programming Manual
For programming information about the OPEN^FILE procedure, see the Guardian Programmer's
Guide.
OPEN^FILE Procedure 913