 | Procedure Division - ENTER - INVOKE |
|
Procedure Division - PERFORM - ROLLBACK |  |
The
MERGE statement combines two or more identically sequenced files on
a set of specified keys, and during the process makes records available,
in merged order, to an output procedure or to an output file.
General Format
Syntax Rules
- File-name-1 must be described in a
sort-merge file description entry in the Data Division.
- Procedure-name-1 represents the name of an output procedure.
- Procedure-name-1 and procedure-name-2 must be section-names.
This restriction is
removed.
-
If the file referenced by
file-name-1 contains variable length records, the size of the records
contained in the files referenced by file-name-2 and file-name-3 must
not be less than the smallest record, nor greater than the largest
record described for file-name-1. If the file referenced by file-name-1
contains fixed length records, the size of the records contained in the
files referenced by file-name-2 and file-name-3 must not be greater than
the largest record described for file-name-1.
- File-name-2, file-name-3, and file-name-4 must be described in a file
description entry, not in a sort-merge file description entry, in the
Data Division.
- The words THRU and THROUGH are equivalent.
- Data-name-1 is a KEY data-name and is subject to the following rules:
- The data items identified by
KEY data-names must be described in records associated with
file-name-1.
- KEY data-names can be qualified.
- The data items identified by KEY data-names must not be variable
length items.
- If file-name-1 has more than one record description, then the
data items identified by KEY data-names need be described in only
one of the record descriptions. The same character position
referenced by a key data-name in one record description entry are
taken as the key in all records of the file.
- None of the data items identified by KEY data-names can be
described by an entry which either contains an OCCURS clause or is
subordinate to an entry which contains an OCCURS clause.
-
KEY data items can be
floating-point items.
-
If the KEY is an
external floating-point item, the key is treated as alphanumeric.
The sequence in which the records are merged depends on the
collating sequence used.
-
If the KEY is an
internal floating-point item, the sequence of key values will be in
numeric order.
- No more than one file-name from a multiple file reel can appear in
the
MERGE statement.
- File-names must not be repeated in the MERGE statement.
- MERGE statements can appear anywhere except in the declaratives
portion of the Procedure Division.
-
If file-name-4 references
an indexed file, the first specification of data-name-1 must be
associated with an
ASCENDING phrase, and the data item referenced by that data-name-1
must occupy the same character positions in its record as the data item
associated with the prime record key for that file.
-
If the
GIVING phrase is specified and the file referenced by file-name-4
contains
variable length records, the size of the records contained in the
file referenced by file-name-1 must not be less than the smallest record
nor greater than the largest record described for file-name-4. If the
file referenced by file-name-4 contains fixed length records, the size
of the records contained in the file referenced by file-name-1 must not
be greater than the largest record described for file-name-4.
- If you want to specify more than 10 file-names in the USING or GIVING
clause, you must use the Compiler directive CALLSORT"EXTSM";
this allows you to specify up to 255 files.
General Rules
- The
MERGE statement merges all records contained on the files
referenced by file-name-2 and file-name-3.
- If the file referenced by file-name-1 contains only
fixed length records, any record in the file referenced by
file-name-2 or file-name-3 containing fewer character positions than
that fixed length is space filled on the right, beginning with the first
character position after the last character in the record, when that
record is released to the file referenced by file-name-1.
- The data-names following the word KEY are listed from left to right
in the MERGE statement in order of decreasing significance without
regard to how they are divided into KEY phrases. The leftmost data-name
is the major key, the next data-name is the next more significant key,
and so on.
- When the
ASCENDING phrase is specified, the merged sequence will be
from the lowest value of the contents of the data items identified
by the key data-names to the highest value, according to the rules
for comparison of operands in a relation condition.
- When the
DESCENDING phrase is specified, the merged sequence will be
from the highest value of the contents of the data items identified
by the key data-names to the lowest value, according to the rules
for comparison of operands in a relation condition.
- When, according to the rules for comparison of operands in relation
condition, the contents of all the key data items of one data record are
equal to the corresponding key data items of one or more other data
records, the order of return of these records:
- follows the order of the associated input files as specified in
the MERGE statement
- is such that all records associated with one input file are
returned prior to the return of records from another input file.
- The collating sequence that applies to the comparison of the
nonnumeric key data items specified is determined at the beginning of
the execution of the
MERGE statement in the following order of precedence:
- First, the collating sequence established by the
COLLATING SEQUENCE phrase, if specified, in that MERGE
statement.
- Second, the collating sequence established as the program
collating sequence.
- The results of the merge operation are undefined unless the records
in the files referenced by file-name-2 and file-name-3 are ordered as
described in the
ASCENDING or
DESCENDING KEY phrases associated with the MERGE statement.
- All the records in the files referenced by file-name-2 and
file-name-3 are transferred to the file referenced by file-name-1. At
the start of execution of the MERGE statement, the files referenced by
file-name-2 and file-name-3 must not be in the open mode. For each of
the files referenced by file-name-2 and file-name-3 the execution of the
MERGE statement causes the following actions to be taken:
- The processing of the file is initiated. The initiation is
performed as if an OPEN statement with the INPUT phrase had been
executed. If an output procedure is specified, this initiation is
performed before control passes to the output procedure.
- The logical records are obtained and released to the merge
operation. Each record is obtained as if a READ statement with the
NEXT and the AT END phrases had been executed.
If the file referenced by file-name-1 is described with variable
length records, the size of any record written to file-name-1 is
the size of that record when it was read from file-name-2 or
file-name-3, regardless of the content of the data item referenced
in the DEPENDING ON phrase of either a RECORD IS VARYING clause or
an OCCURS clause specified in the sort-merge file description
entry for file-name-1.
For a relative file, the content of the relative data key item
is undefined after the execution of the MERGE statement.
- The processing of the file is terminated. The termination is
performed as if a CLOSE statement without optional phrases had been
executed. If an output procedure is specified, this termination is
not performed until after control passes the last statement in the
output procedure.
These implicit functions are performed such that any associated
USE AFTER EXCEPTION/ERROR procedures are executed.
The value of the data item referenced by the DEPENDING ON phrase
of a RECORD IS VARYING clause specified in the file description
entry for file-name-2 or file-name-3 is undefined upon completion
of the
MERGE statement.
- The output procedure can consist of any procedure needed to select,
modify or copy the records that are made available one at a time by the
RETURN statement in merged order from the file referenced by
file-name-1. The range includes all statements that are executed as the
result of a transfer of control by CALL, EXIT, GO TO, and PERFORM
statements in the range of the output procedure, as well as all
statements in declarative procedures that are executed as a result of
the execution of statements in the range of the output procedure. The
range of the output procedure must not cause the execution of any MERGE,
RELEASE, or SORT statement. (See the section Explicit and Implicit
Specifications in the chapter Concepts of the COBOL Language.)
- If an output procedure is specified, control passes to it during
execution of the MERGE statement. The compiler inserts a return
mechanism at the end of the last statement in the output procedure. When
control passes the last statement in the output procedure, the return
statement provides for termination of the merge, and then passes control
to the next executable statement after the MERGE statement. Before
entering the output procedure, the merge procedure reaches a point at
which it can select the next record in merged order when requested. The
RETURN statements in the output procedure are the requests for the next
record.
- During the execution of the output procedure, no statement can be
executed manipulating the file referenced by, or accessing the record
area associated with, file-name-2, file-name-3, or file-name-4.
- If the
GIVING phrase is specified, all the merged records are written on
the file referenced by file-name-4 as the implied output procedure for
the MERGE statement. At the start of execution of the MERGE statement,
the file referenced by file-name-4 must not be in the open mode. For
each of the files referenced by file-name-4, the execution of the
MERGE statement causes the following actions to be taken:
- The processing of the file is initiated. The initiation is
performed as if an OPEN statement with the OUTPUT phrase had been
executed.
- The merged logical records are returned and written onto the
file. Each record is written as if a WRITE statement without any
optional phrases had been executed.
If the file referenced by file-name-4 is described with variable
length records, the size of any record written to file-name-4 is
the size of that record when it was read from file-name-1,
regardless of the content of the data item referenced in the
DEPENDING ON phrase of either a RECORD IS VARYING clause or an
OCCURS clause specified in the file description entry for
file-name-4.
For a relative file, the relative key data item for the first
record returned contains the value "1"; for the second
record returned, the value "2", and so on. The content
of the relative key data item is undefined after execution of the
MERGE statement.
- The processing of the file is terminated. The termination is
performed as if a CLOSE statement without optional phrases had been
executed.
These implicit functions are performed such that any associated
USE AFTER EXCEPTION/ERROR procedures are executed; however, the
execution of such a USE procedure must not cause the execution of
any statement manipulating the file referenced by, or accessing
the record area associated with, file-name-4. On the first attempt
to write beyond the externally defined boundaries of the file, any
USE AFTER EXCEPTION/ERROR procedure specified for the file is
executed; if control is returned from the USE procedure or if no
such USE procedure is specified, the processing of the file is
terminated as in paragraph 11c above.
The value of the data item referenced by the DEPENDING ON phrase
of a RECORD IS VARYING clause specified in the file description
entry for file-name-1 is undefined upon completion of the MERGE
statement for which the GIVING phrase is specified.
- If the file referenced by file-name-4 contains only fixed length
records, any record in the file referenced by file-name-1 containing
fewer character positions than that fixed length is space filled on the
right, beginning with the first character position after the last
character in the record, when that record is returned to the file
referenced by file-name-4.
- Segmentation, as defined in the chapter Segmentation in your
Language Reference - Additional Topics, can be applied
to programs containing the
MERGE statement. However, the following restrictions apply:
- If the MERGE statement appears in a section that is not in an
independent segment, then any output procedure referenced by that
merge statement must appear:
- totally within non-independent segments, or
- wholly contained in a single independent segment.
- If a MERGE statement appears in an independent segment, then any
output procedure referenced by that MERGE statement must be
contained:
- totally within non-independent segments, or
- wholly within the same independent segment as that MERGE
statement.
-
The
SORT-RETURN
special register is available to source elements with a MERGE
statement. It contains a return code of 0 (successful) or 16
(unsuccessful) at the completion of the merge operation. You can set the
special register to 16 in the output procedure to terminate a merge
operation before all records are processed. The operation is terminated
on the next RETURN statement.
The MOVE statement transfers data, in accordance with the rules of
editing, to one or more data areas.
General Formats
Format 1
Format 2
Directives
- In addition to Compiler directives which provide flagging and modify
the reserved word list, the following directives may impact either the
syntax or semantics described in this section.
- BYTE-MODE-MOVE - impacts the behavior of MOVE statements in which
the sending and receiving items share a part of their storage (that
is, overlapping moves).
- DBCS (DBSPACE) - impacts what characters are used for space
filling DBCS receiving items.
- DE-EDIT - controls whether the value of numeric-edited sending
fields is determined by their PICTURE clause or not.
- TRUNC - determines when the sending item includes a value larger
than a binary receiving values size, whether truncation occurs based
on the storage available or the PICTURE clause.
Syntax Rules
All Formats
- Identifier-1 and literal represent the sending area; identifier-2
represents the receiving area.
-
A data item must not be
specified as an operand of a MOVE statement, if its usage is one of the
following:
INDEX
OBJECT-REFERENCE
POINTER,
PROCEDURE-POINTER
ENTRY-POINTER,
MONITOR-POINTER, MUTEX-POINTER, SEMAPHORE-POINTER or THREAD-POINTER.
-
If either the sending or
receiving item is a DBCS (USAGE DISPLAY-1) item, then both must be DBCS
items. The figurative constant SPACE can be the DBCS sending item.
Format 1
-
When Format 1 is
specified, all identifiers can be either group or elementary items. The
data in the sending area is moved into the data item referenced by each
identifier-2 in the order in which it is specified.
-
Identifier-1 may be a
numeric function-identifier.
Format 2
- CORR is an abbreviation for CORRESPONDING.
- When the
CORRESPONDING phrase is used, all identifiers must be group items.
-
The following items can
be part of a group that is referenced in a MOVE CORRESPONDING statement;
however, no movement of this item will take place:
POINTER,
PROCEDURE-POINTER
OBJECT-REFERENCE
EVENT-POINTER,
MONITOR-POINTER, MUTEX-POINTER, SEMAPHORE-POINTER, THREAD-POINTER.
- A pointer data item can be part of a group that is referenced in a
MO
VE CORRESPONDING statement; however, no movement of the pointer
data item will take place.
General Rules
All Formats
-
If identifier-1 is a
numeric function-identifier, then identifier-2 must be either a numeric
or numeric edited item.
- The data designated by the literal or identifier-1 is moved to the
data item referenced by each identifier-2, in the order in which it is
specified. The rules referring to identifier-2 also apply to the other
receiving areas. Any subscripting or indexing associated with
identifier-2, is evaluated immediately before the data is moved to the
respective data item.
If identifier-1 is
reference modified, subscripted, or is a function- identifier, the
reference modifier, subscript, or function-identifier is evaluated
only once, immediately before data is moved to the first of the
receiving operands.
The result of the
statement:
MOVE a(b) TO b, c(b)
is equivalent to:
MOVE a(b) TO temp
MOVE temp TO b
MOVE temp TO c(b)
where temp is an intermediate result item provided by
your COBOL system.
- Any MOVE in which the sending and receiving items are both elementary
items is an elementary move. Every elementary item belongs to one of the
following categories: numeric, alphabetic, alphanumeric, numeric edited,
alphanumeric edited
or floating-point.
These categories are described in the PICTURE clause. Numeric
literals belong to the category numeric, and nonnumeric literals
belong to the category alphanumeric. The figurative constant ZERO
belongs to the category numeric when moved to a numeric or
numeric-edited item. The figurative constant ZERO belongs to the
category alphanumeric in all other cases. The figurative constant
SPACE belongs to the category alphabetic. All other figurative
constants belong to the category alphanumeric.
The following rules apply to an elementary move between these
categories:
-
- The figurative constant SPACE, or an alphanumeric edited, or
alphabetic data item must not be moved to a numeric or numeric
edited data item.
- A numeric edited data item must not be moved to a numeric or
numeric edited data item.
This restriction
is removed.
- A numeric literal, the figurative constant ZERO, a numeric data
item or a numeric edited data item must not be moved to an
alphabetic data item.
- A non-integer numeric literal or a non-integer numeric data item
must not be moved to an alphanumeric or alphanumeric-edited data
item.
- All other elementary moves are legal and are performed according
to the rules given in General Rule 5.
- Any necessary conversion of data from one form of internal
representation to another takes place during legal elementary moves,
along with any editing specified for
,or de-e
diting implied by,
the receiving data item:
- When an alphanumeric edited or alphanumeric item is a receiving
item, alignment and any necessary space filling takes place as
defined in the section Standard Alignment Rules in the
chapter Concepts of the COBOL Language. If the size of the
sending item is greater than the size of the receiving item, the
excess characters are truncated on the right after the receiving
item is filled. If the sending item is described as being signed
numeric, the operational sign will not be moved; if the operational
sign occupies a separate character position (see the section The
SIGN Clause earlier in this chapter), that character will not be
moved and the size of the sending item will be considered to be one
less than its actual size (in terms of standard data format
characters).
- When a numeric or numeric edited item is the receiving item,
alignment by decimal point and any necessary zero-filling takes
place as defined in the section Standard Alignment Rules in
the chapter Concepts of the COBOL Language, except where
zeros are replaced because of editing requirements.
When the sending
operand is numeric edited, de-e
diting is implied to establish the operand's unedited
numeric value, which can be signed; then the unedited numeric
value is moved to the receiving field. The effect of de-editing
depends on the setting of the DE-EDIT Compiler directive
When a signed numeric item is the receiving item, the sign of
the sending item is placed in the receiving item. (See the section
The SIGN Clause earlier in this chapter.) Conversion of
the representation of the sign takes place as necessary. If the
sending item is unsigned, a positive sign is generated for the
receiving item.
When an unsigned numeric item is the receiving item, the
absolute value of the sending item is moved and no operational
sign is generated for the receiving item.
When a data item described as alphanumeric is the sending item,
data is moved as if the sending item were described as an unsigned
numeric integer.
When the receiving item is numeric or numeric-edited and the
sending item is defined as alphanumeric, if the content of the
sending item is not an integer, the results of the move are
undefined. If the alphanumeric sending item is a literal whose
contents do not represent an integer, an error will be reported,
and zero moved to the target. (See the section Incompatible
Data earlier in this chapter.)
When the numeric data
item is the sending item the action of the move will be such that
a reverse of the move would cause the same value to appear in the
numeric edited field (except or truncation). If the data item
contains data which does not conform to the edited picture, zero
is moved to the target.
- When a receiving field is described as alphabetic, justification
and any necessary space-filling takes place as defined in the
section Standard Alignment Rules in the chapter Concepts
of the COBOL Language. If the size of the sending item is
greater than the size of the receiving item, the excess characters
are truncated on the right after the receiving item is filled.
-
When the receiving
field is floating-point, the sending item is converted first to
internal floating-point and then moved. When data is moved to or
from an external floating-point item, the data is converted first to
or from its equivalent internal floating-point value.
-
When the receiving
field is DBCS the sending item must also be DBCS; no conversion
takes place. If the sending and receiving items are not the same
size the data item will be either truncated or padded with DBCS
spaces on the right.
- Any move that is not an elementary move is treated exactly as if it
were an alphanumeric to alphanumeric elementary move, except that no
conversion of data from one form of internal representation to another
takes place. In such a move, the receiving area will be filled without
consideration for the individual elementary or group items contained in
either the sending or receiving area, except as noted in the General
Rules of the OCCURS clause.
- Table 14-1 summarizes the legality of the various types of MOVE
statements. The general rule reference indicates the rule that prohibits
the move or the behavior of a legal move.
Format 2
- If the
CORRESPONDING phrase is used, selected items in identifier-1 are
moved to selected items in identifier-2, according to the rules given in
the section The CORRESPONDING Phrase earlier in this chapter.
The results are the same as if the user had referred to each pair of
corresponding identifiers in separate
MOVE statements.
The process is repeated
for each destination group.
Table 14-1:
MOVE Statement Data Categories
| Category of Sending Item |
Category of Receiving
Data Items1 |
| Alphabetic |
Alphanumeric-Edited/ Alpha-numeric |
Numeric Integer/Non-Integer |
Numeric-Edited External/Internal
Floating Point |
DBCS |
| Alphabetic |
Yes/4c |
Yes/4a |
No/3a |
No/3a |
No/4e |
| Alphanumeric |
Yes/4c |
Yes/4a |
Yes/4b2 |
Yes/4b |
No/4e |
| Alphanumeric-Edited |
Yes/4c |
Yes/4a |
No/3a |
No/3a |
No/4e |
| Numeric Integer |
No/3b |
Yes/4a |
Yes/4b |
Yes/4b |
No/4e |
| Numeric Non-Integer |
No/3b |
No/3c |
Yes/4b |
Yes/4b |
No/4e |
| Numeric-Edited |
No/3b |
Yes/4a |
Yes/4b |
Yes/4b |
No/4e |
| DBCS |
No/4e |
No/4e |
No/4e |
No/4e |
Yes/4e |
- The relevant rule number is quoted in these columns
- An error will be reported if a non-integer alphanumeric literal
sending item is used
The MULTIPLY statement causes numeric data items to be multiplied and
sets the values of data items equal to the results.
General Formats
Format 1
Format 2
Syntax Rules
All Formats
- Each identifier must refer to a numeric elementary item, except that
in Format 2 each identifier following the word GIVING must refer to
either an elementary numeric item or an elementary numeric edited item.
- Each literal must be a numeric literal.
- The
composite of
operands, which is that hypothetical data item resulting from the
superimposition of all receiving data items aligned on their decimal
points, must not contain more than 18 digits.
-
Floating-point data items
and literals can be used anywhere a numeric data item or literal can be
specified.
General Rules
All Formats
- See the sections The ROUNDED Phrase, The ON SIZE ERROR
Phrase, Arithmetic Statements, Overlapping Operands and Multiple
Results In Arithmetic Statements in this chapter.
Format 1
- When Format 1 is used, the value of identifier-1 or literal-1 is
multiplied by the value of identifier-2. The value of the multiplier
(identifier-2) is replaced by this product; similarly for each
successive occurrence of identifier-2 in the left-to-right order in
which identifier-2 is specified.
Format 2
- When Format 2 is used, the value of identifier-1 or literal-1 is
multiplied by identifier-2 or literal-2 and the result is stored in the
data item referenced by each identifier-3.
The NEXT SENTENCE statement transfers control to the next COBOL
sentence, that is, following the next period. It does not transfer control
to the logically next COBOL verb as occurs with the
CONTINUE verb.
General Format
Syntax Rules
- The NEXT SENTENCE statement can be used anywhere a conditional
statement or an imperative-statement can be used.
General Rules
- The NEXT SENTENCE statement redirects the flow of execution to the
logically next COBOL verb following the next period.
The NOTE statement introduces a sentence or paragraph that will be
treated as comments.
General Format
Syntax Rules
- The character-string can be any combination of characters from the
computer character set.
General Rules
- If a NOTE statement is the first sentence of a paragraph, the entire
paragraph is treated as comment.
- If a NOTE statement appears as other than the first sentence of a
paragraph, text up to the next separator period is treated as comment.
The ON statement allows selective execution of procedural statements on
a periodic basis.
General Format
Syntax Rules
- Identifier-1, identifier-2 and identifier-3 must describe unsigned
integer numeric elementary items.
- Literal-1, literal-2 and literal-3 must be unsigned numeric literals.
General Rules
- Prior to the first execution of each ON statement
, a counter, implicitly defined for that ON statement (the
implicit-ON-counter), is initialized to be zero.
- Identifier-1, identifier-2 and identifier-3 should, if specified,
contain positive integer values at the time of execution of the ON
statement. Varying these values between executions of the ON statement
will affect subsequent executions of the ON statements.
- The implicit ON counter cannot be affected in any way other than by
transfer of
execution flow to that ON statement. (The ON counter of a called
program can only be reset by the cancelling of that program; execution
of the EXIT PROGRAM statement and subsequent CALL of the program without
intervening CANCEL has no effect upon the implicit ON counter value.)
- The following value-list is then evaluated:
- the current value of identifier-1 or literal-1,
- a sequence of values being the results of repeatedly adding the
current value of identifier-2 or literal-2 to the current value of
identifier-1 or literal-1 until the value of identifier-3 or
literal-3 is reached.
The implicit-ON-counter is then compared with each of this list of
values. If an equality is found, then imperative-statement-1 is
executed. If no equality is found, then imperative-statement-2, if
specified, is executed.
The
OPEN statement initiates the processing of files. It also performs
checking and/or writing of labels and other input-output operations.
The REVERSED phrase of the
OPEN statement is classed as an obsolete element in the ANSI'85 standard
and is scheduled to be deleted from the next full revision of the ANSI
Standard.
All dialects in this COBOL
implementation fully support this syntax. The FLAGSTD Compiler directive
can be used to detect all occurrences of this syntax.
Although it is a part of the
standard COBOL definition, the
REVERSED phrase of the OPEN statement is explicitly excluded from
the X/Open COBOL language definitions and should not be used in a
conforming X/Open COBOL source program.
The OPEN statement allocates
system resources for a synchronization data item and initializes the data
item.
General Formats
Format 1 (Record Sequential Files)
Format 2 ( Line Sequential, Relative And Indexed Files)
where sharing-phrase is:
Format 3 (Synchronization
Data Items)
Syntax Rules
All Formats (All Files)
- The files referenced in the
OPEN statement need not all have the same organization or access.
-
If SHARING ALL is
specified and the INPUT phrase is not specified, the LOCK MODE clause
must be specified in the file control entry for file-name-1.
Format 1 (Record Sequential Files)
-
NO
REWIND is documentary only.
- The I/
O phrase can be used only for
disk files.
- The
EXTEND phrase must be used only for files for which the LINAGE
clause has not been specified.
- The EXTEND phrase must not be specified with multiple file reels.
Format 2 (
Line
Sequential,
Relative and Indexed Files)
-
The EXTEND phrase can be
used for files in sequential access mode.
-
The SHARING phrase must
not be specified for files with line sequential organization.
Format 3
(Synchronization Data Items)
-
Identifier-1 must reference
an elementary data item with a USAGE of EVENT-POINTER, MONITOR-POINTER,
MUTEX-POINTER or SEMAPHORE-POINTER.
General Rules
Formats 1
and 2 (All Files)
- Prior to the successful execution of an OPEN statement for a given
file, no statement (except for a SORT or MERGE statement with the USING
or GIVING phrases) can be executed that references that file, either
explicitly or implicitly.
-
The successful execution
of an OPEN statement determines the availability of the file and results
in the file connector referenced by the file-name being in an open mode.
The successful execution of an OPEN statement associates the file with
the file-name through a file connector.
The key words INPUT, OUTPUT, I-O, and EXTEND specify the type of
input-output operations intended for the file through the file
connector and establish the open mode. (See table 14-4, Permissible
Combinations of Statements and OPEN Modes.)
A file is available if it is physically present and is recognized by
the file handling system. Table 14-2, Opening Available and
Unavailable Files (file not currently open), shows the results of
opening available and unavailable files that are not currently open.
Table 14-3, Opening Available Shared Files that are Currently Open by
Another File Connector, shows the results of opening available and
unavailable files that are currently open by another file connector.
Table 14-2: Opening Available and Unavailable Files (file not
currently open)
| Open Mode |
File is available |
File is unavailable |
| INPUT |
Normal open |
Open is unsuccessful |
| INPUT (optional file) |
Normal open |
Normal open; the first read causes the at end condition or
invalid key condition |
| I-O |
Normal open |
Open is unsuccessful |
| I-O (optional file) |
Normal open |
Open causes the file to be created |
| OUTPUT |
Normal open; the file contains no records |
Open causes the file to be created |
| EXTEND |
Normal open |
Open is unsuccessful |
| EXTEND (optional file) |
Normal open |
Open causes the file to be created |
Table 14-3: Opening available shared files that are currently
open by another file connector
Open request |
Most restrictive existing
sharing mode and open mode |
| sharing with no other |
sharing with read only |
sharing with all other |
extend
I-O
input
output |
extend
I-O
output |
input |
extend
I-O
output |
input |
| SHARING WITH NO OTHER |
EXTEND
I-O
INPUT
OUTPUT |
Unsuccessful open |
Unsuccessful open |
Unsuccessful open |
Unsuccessful open |
Unsuccessful open |
| SHARING WITH READ ONLY |
EXTEND
I-O |
Unsuccessful open |
Unsuccessful open |
Unsuccessful open |
Unsuccessful open |
Normal open |
| INPUT |
Unsuccessful open |
Unsuccessful open |
Normal open |
Unsuccessful open |
Normal open |
| OUTPUT |
Unsuccessful open |
Unsuccessful open |
Unsuccessful open |
Unsuccessful open |
Unsuccessful open |
| SHARING WITH ALL OTHER |
EXTEND
I-O |
Unsuccessful open |
Unsuccessful open |
Unsuccessful open |
Normal open |
Normal open |
| INPUT |
Unsuccessful open |
Normal open |
Normal open |
Normal open |
Normal open |
| OUTPUT |
Unsuccessful open |
Unsuccessful open |
Unsuccessful open |
Unsuccessful open |
Unsuccessful open |
- The successful execution of an OPEN statement makes the associated
record area available
.
- In Table 14-2, "X" at an intersection indicates that
the specified statement, used in the access mode given for that row, can
be used with the open mode given at the top of the column.
Table 14-4: Permissible Combinations of Statements and OPEN
Modes
| File Access Mode |
OPEN Mode |
| Statement |
Input |
Output |
Input-Output |
Extend |
| Sequential |
READ |
X |
|
X |
|
| WRITE |
|
X |
|
X |
| REWRITE |
|
|
X |
|
| Random (Non-Sequential
Files) |
READ |
X |
|
X |
|
| WRITE |
|
X |
X |
|
| REWRITE |
|
|
X |
|
| START |
|
|
|
|
| DELETE |
|
|
X |
|
| Dynamic (Non-Sequential
Files) |
READ |
X |
|
X |
|
| WRITE |
|
X |
X |
|
| REWRITE |
|
|
X |
|
| START |
X |
|
X |
|
| DELETE |
|
|
X |
|
Note: The START and DELETE statements can not be used with
record
or line
sequential files.
-
If the
WITH LOCK phrase is specified, the OPEN statement acquires a
lock on the whole file. (This is equivalent to specifying LOCK
MODE IS EXCLUSIVE in the SELECT statement for the file. See the section
The SELECT Statement in this chapter.)
-
If, during the execution of
an
OPEN statement, a file attribute conflict occurs, the execution of
the OPEN statement is unsuccessful. Your COBOL system defines which of
the
fixed file attributes are validated during the execution of the
OPEN statement. See your file handling documentation for more details.
The validation of fixed file attributes can vary depending on the
organization and/or storage medium of the file.
-
A file can be opened with
the INPUT, OUTPUT, EXTEND and I/O phrases in the same run unit.
Following the initial execution of an OPEN statement for a file
connector, each subsequent OPEN statement execution for that same file
connector must be preceded by the execution of a CLOSE statement for
that file connector, even if the file is optional.
- Execution of the
OPEN statement does not obtain or release the first data record.
- The external name of the file specified in the SELECT clause for a
file is processed as follows:
- When the INPUT phrase is specified, execution of the OPEN
statement causes the name to be checked in accordance with the
operating system conventions for opening files for input.
- When the OUTPUT phrase is specified, execution of the OPEN
statement causes the name to be checked in accordance with the
operating system conventions for opening files for output.
- The file description entry for file-name-1, file-name-2, file-name-3,
and file-name-4 must be equivalent to that used when this file was
created.
- For files being opened with the
INPUT or
I/O phrase, the OPEN statement sets the
file position indicator to the first record currently existing in
the file for indexed and sequential files, and record position one for
relative files. If no records exist in the file, the file position
indicator is set such that the next executed READ statement for an
indexed or sequential file will result in an
AT END condition. If the file does not exist, OPEN INPUT will
cause an error status, unless the file is optional.
- When the I/O phrase is specified and the
LABEL RECORDS clause indicates lab
el records are present, the execution of the OPEN statement
includes the following steps:
- The labels are checked in accordance with the operating
system-specified conventions for input-output label checking.
- The new labels are written in accordance with the operating
system-specified conventions for input-output label writing.
- Upon successful execution of an OPEN statement with the OUTPUT phrase
specified, a file is created. At that time the associated file contains
no data records. If a file of the same name exists it will be deleted.
If write-protected an error will occur.
-
When the
EXTEND phrase is specified, the
OPEN statement positions the file immediately after the last
logical record for that file. The last logical record for a
sequential file is the last record written in the file. In a relative
file it is the currently existing record with the highest relative
record number, and in an indexed file it is the currently existing
record with the highest prime key value.
- Execution of the OPEN statement causes the value of the
FILE STATUS data item to be updated (see the section I/O
Status earlier in this chapter).
-
When
LOCK MODE IS EXCLUSIVE is specified in the SELECT/ ASSIGN
statement of a file, successful execution of an OPEN statement of that
file locks the file exclusively to that run unit.
-
When LOCK
MODE IS AUTOMATIC or
LOCK MODE IS MANUAL is specified in the SELECT/ASSIGN statement of
a file, the file that is referred to is shareable. More than one run
unit can successfully open such a file.
-
A file opened for
OUTPUT, and relative and indexed files opened EXTEND, are
implicitly defined as files with an
exclusive lock, that is, they are not shareable.
-
Only shareable files opened
for I/O can acquire
record locks.
- If execution of the OPEN statement is unsuccessful, the physical file
is not affected and the following actions take place in this order:
- A value is placed in the I/O status associated with file-name to
indicate the condition that caused the OPEN statement to be
unsuccessful.
- Any applicable USE AFTER EXCEPTION procedure is executed. (See
the section The USE Statement in this chapter.)
- The I/O phrase permits the opening of a file for both input and
output operations. If the file does not exist, the following rules
apply:
- If the
OPTIONAL phrase is specified, the file is created
- If the NOT OPTIONAL phrase is specified, an error occurs
- If neither phrase is specified, and the
directive
OPTIONAL-FILE was specified when the source element was
compiled, the file is created.
- If neither phrase is specified, and the directive NOOPTIONAL-FILE
was specified when the source element was compiled, an error occurs.
- If an input file is designated with the
OPTIONAL phrase in its SELECT clause, when the file is opened
there is an interrogation for the presence or absence of this file. If
the file is not present, the first READ statement for this file causes
the AT END condition to occur.
- When the
EXTEND phrase is specified, the
OPEN statement positions the file immediately following the last
logical record of that file. Subsequent WRITE statements referencing the
file will add records to the file as though the file had been opened
with the OUTPUT phrase. If the file does not exist it will be created.
-
When the EXTEND phrase is
specified and the
LABEL RECORDS clause in this file's FD indicates label records are
present, the execution of the OPEN statement includes the following
steps:
- The beginning file labels are processed only in the case of a
single reel/unit file.
- The beginning reel/unit labels on the last existing reel/unit are
processed as though the file was being opened with the
INPUT phrase.
- The existing ending file labels are processed as though the file
is being opened with the INPUT phrase. These labels are then
deleted.
- Processing then proceeds as though the file had been opened with
the OUTPUT phrase.
- The I
/O phrase permits the
opening of a file for both input and output operations,
except files with
ORGANIZATION LINE SEQUENTIAL.
If the file does not exist, it will be created and used as an empty
file for input
unless NOT OPTIONAL was
specified in the SELECT statement.
An attempt to READ from the newly created file will cause an error.
-
The SHARING phrase can be
specified only for shared files. (See
Sharing mode.)
-
The SHARING phrase
specifies what operations may be performed on the file through other
file connectors sharing the file. (See
Sharing mode.)
-
The SHARING phrase
overrides any SHARING clause in the file control entry of the file
connector associated with the file-name. If there is no SHARING phrase
on the OPEN statement, then file sharing is completely specified in the
file control entry. If neither a SHARING phrase on the OPEN statement
nor a SHARING clause in the file control entry is specified, the sharing
mode is established for the file connector in accordance with
Sharing mode.
Format 1 (Record Sequential Files)
- If the storage medium for the file permits rewinding, the following
rules apply:
- Execution of the OPEN statement causes the file to be positioned
at its beginning.
- When the
REVERSED phrase is specified, the file is positioned at its
end by execution of the OPEN statement.
- When the
REVERSED phrase is specified, the subsequent READ statements for
the file make the data available in reversed order; that is, starting
with the
last record.
Format 2 (Line Sequential Files)
-
I/O mode is not allowed for
line sequential files unless the
REWRITE-LS Compiler
directive is set.
Format 3 (Synchronization Data
Items)
- Prior to the successful execution of an OPEN statement for a given
synchronization data item, no statement can be executed that references
that data item.
- The successful execution of an OPEN statement determines the
availability of the synchronization data item.
- Execution of the OPEN statement causes the RETURN-CODE special
register to be updated with one of the values specified for the
CBL_MUTEX APIs.
- Following the initial execution of an OPEN statement for a
synchronization data item, each subsequent OPEN statement execution for
that same data item must be preceded by the execution of a CLOSE
statement for that data item.
- If identifier-1 references an event data item, the execution of the
OPEN statement initializes the data item to FALSE.
- If identifier-1 references a monitor data item, the execution of the
OPEN statement initializes the monitor to NOT BROWSING, NOT READING, and
NOT WRITING.
- If identifier-1 references a mutex data item, the execution of the
OPEN statement initializes the data item to OFF.
- If identifier-1 references a semaphore data item, the execution of
the OPEN statement initializes the data item to zero.
Copyright © 2000 MERANT International Limited. All rights reserved.
This document and the proprietary marks and names
used herein are protected by international law.
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