Guardian Procedure Calls Reference Manual

USERIOBUFFER_ALLOW_ Procedure
Summary
Syntax for C Programmers
Syntax for TAL Programmers
Considerations
Summary
The USERIOBUFFER_ALLOW_ procedure dynamically sets the process behavior to be the same as
if the objectfile flag "allow_user_buffers" were set in eld, provided it is called before opening
any files. Its impact is limited to files opened by FILE_OPEN_ after the procedure is called. It has
no impact on I/O operations initiated on files opened before the call or files opened by OPEN.
Syntax for C Programmers
void USERIOBUFFER_ALLOW_ ( void );
Syntax for TAL Programmers
CALL USERIOBUFFER_ALLOW_;
Considerations
• For NSAA systems, the default is system buffers for I/O operation on all files. Calling the
USERIOBUFFER_ALLOW_ procedure enables user buffers for I/O operations (for example
READX or WRITEX) on all subsequent files opened by FILE_OPEN_ procedure. The
USERIOBUFFER_ALLOW_ procedure does not affect the buffer status of files opened by the
OPEN procedure, which uses system buffers for its I/O buffers. SETMODE function 72 can
enable user buffers on the files that are already opened.
• The USERIOBUFFER_ALLOW_ procedure is useful on NSAA systems and can be called on
any system (H-series or J-series). Once the procedure is called, the USERIOBUFFER_ALLOW_
setting cannot be turned off.
• The user buffers being enabled does not guarantee that the user buffers will be used; the
system is still free to select the most efficient buffers to use. In practice, I/O less than 4096
bytes will system buffers.
• The user buffers should be in multiples of page size and page aligned for optimal performance.
They must have at least eight-byte alignment.
• When using user buffers, read or write operations must not be performed on nowait user
buffers until the AWAITIO procedure is called.
USERIOBUFFER_ALLOW_ Procedure 1477