COBOL Manual for TNS/E Programs (H06.03+)

Disk Input and Output
HP COBOL Manual for TNS/E Programs—520347-003
28-34
Structured Files
HP COBOL Fast I-O
Fast I-O is an HP COBOL enhancement in input-output performance beyond that of
sequential block buffering or buffered cache. With HP COBOL Fast I-O, the
HP COBOL run-time routines use an auxiliary block buffer and perform the blocking
and deblocking in local storage. This process operates 2 or 3 times faster than when
the operating environment performs the blocking and deblocking operations.
HP COBOL Fast I-O is available if the HP COBOL program and the structured file
upon which it is to operate meet these criteria:
•
The file description includes a RESERVE clause with a number specifying the
number of blocks to buffer. The number must be greater than 2.
•
The file description does not include a LINAGE clause or a CODE-SET clause.
•
The file was not opened with time limits (as with the TIME LIMITS phrase in the
OPEN statement).
•
The program is not compiled with the NONSTOP directive.
•
The specifications in the OPEN statement, or the attributes derived during the
open operation by some other means (such as from a TACL ASSIGN command),
conform to:
°
The open mode is INPUT or OUTPUT.
°
If the open mode is INPUT, the exclusion mode is PROTECTED or
EXCLUSIVE.
°
If the open mode is OUTPUT, the exclusion mode is EXCLUSIVE.
If all of the preceding qualifications are satisfied at run time, HP COBOL Fast I-O is
used only if memory resources are available. For a file opened for output, the loader
creates the file. The loader is also used by FUP, SQL/MP, and other products. The
loader manages its own extended data segment to write the file. The loader requires
local storage, which is allocated by the run-time system. The amount of local storage is
approximately 800 bytes (the exact amount depends on the type of the file and other
factors). If the necessary storage is not available, the OPEN statement returns file
status “07” and buffered cache is used to write the file.
Note. HP COBOL Fast I-O is not recommended for an indexed file that has had many records
inserted or deleted since it was created. If you want to use HP COBOL Fast I-O on such a file,
first use FUP RELOAD to reorganize it.