6.2.26 OPEN Statement
The OPEN statement initiates the processing of files. It also checks and/or writes labels.
___ Format 1--Sequential Files _________________________________________
| |
| >>__OPEN_____________________________________________________________> |
| |
| <________________________________________________________ |
| <_________________________________________ | |
| >____ _INPUT____file-name-1__ ________________________ _|_ _|_______>< |
| | | (1) | | |
| | |_REVERSED_______________| | |
| | | (1)| | |
| | |_ ______ __NO REWIND____| | |
| | |_WITH_| | |
| | <______________________________________ | |
| |_OUTPUT____file-name-2__ _____________________ _|___| |
| | |_ ______ __NO REWIND_| | |
| | |_WITH_| | |
| | <_____________ | |
| |_I-O____file-name-3_|_______________________________| |
| | <_____________ | |
| |_EXTEND____file-name-4_|____________________________| |
| |
| Note: |
| (1) Under OS/390, the REVERSED and WITH NO REWIND phrases are not |
| valid for VSAM files. Under AIX, OS/2, and Windows, the REVERSED |
| and WITH NO REWIND phases are treated as a comment. |
| |
|________________________________________________________________________|
___ Format 2--Indexed and Relative Files _______________________________
| |
| <_____________________________ |
| <_____________ | |
| >>__OPEN____ _INPUT____file-name-1_|__ _|___________________________>< |
| | <_____________ | |
| |_OUTPUT____file-name-2_|_| |
| | <_____________ | |
| |_I-O____file-name-3_|____| |
| | <_____________ | |
| |_EXTEND____file-name-4_|_| |
| |
|________________________________________________________________________|
X ___ Format 3--Line Sequential Files (Workstation Only) _________________ X | | X | <_____________________________ | X | <_____________ | | X | >>__OPEN____ _INPUT____file-name-1_|__ _|___________________________>< | X | | <_____________ | | X | |_OUTPUT____file-name-2_|_| | X | | <_____________ | | X | |_EXTEND____file-name-4_|_| | | | |________________________________________________________________________|At least one of the phrases, INPUT, OUTPUT, I-O, or EXTEND, must be specified with the OPEN key word. The INPUT, OUTPUT, I-O, and EXTEND phrases can appear in any order.
- INPUT
-
Permits opening the file for input operations.
- OUTPUT
-
Permits opening the file for output operations. This phrase can be
specified when the file is being created.
Note: Do not specify OUTPUT for files that:- Contain records. The file will be replaced by new data. If the
OUTPUT phrase is specified for a file that already contains
records, the data set must be defined as reusable and cannot have
an alternate index. The records in the file will be replaced by
the new data and any ALTERNATE RECORD KEY clause in the SELECT
statement will be ignored.
- Under OS/390, are defined with a DD dummy card. Unpredictable
results can occur.
- Contain records. The file will be replaced by new data. If the
OUTPUT phrase is specified for a file that already contains
records, the data set must be defined as reusable and cannot have
an alternate index. The records in the file will be replaced by
the new data and any ALTERNATE RECORD KEY clause in the SELECT
statement will be ignored.
- I-O
-
Permits opening the file for both input and output operations. The
I-O phrase can be specified only for files assigned to direct access
devices.
X >_Workstation_> Under AIX, OS/2, and Windows, the I-O phrase is not
X valid for line sequential files. <_Workstation_< - EXTEND
-
Permits opening the file for output operations.
The EXTEND phrase is only allowed for sequential access files if the
X new data is written in ascending sequence. As an IBM extension, the
X EXTEND phrase is allowed for files that specify the LINAGE clause.
Under OS/390, for QSAM files, do not specify the EXTEND phrase for a multiple file reel.
If you want to append to a file, but are unsure if the file exists, use the SELECT OPTIONAL clause before OPENing the file in EXTEND mode. The file will be created or appended to, depending on whether the file exists. - file-name-1, file-name-2, file-name-3, file-name-4
-
Designates a file upon which the OPEN statement is to operate. If
more than one file is specified, the files need not have the same
organization or access. Each file-name must be defined in an FD entry
in the Data Division, and must not name a sort or merge file. The FD
entry must be equivalent to the information supplied when the file was
defined.
- REVERSED
-
>_Host_> Under OS/390 and VM, the REVERSED phrase is only valid for
sequential single reel files. It is not valid for VSAM files.
If the concept of reels has no meaning for the storage medium (for example, a direct access device), the REVERSED and NO REWIND phrases do not apply. <_Host_<
>_Workstation_> Under AIX, OS/2, and Windows, the REVERSED phrase is treated as a comment. <_Workstation_< - NO REWIND
-
>_Host_> Under OS/390 and VM, the NO REWIND phrase is only valid for
sequential single reel files. It is not valid for VSAM files.
<_Host_<
>_Workstation_> Under AIX, OS/2, and Windows, the NO REWIND phrase is treated as a comment. <_Workstation_<
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