1. The successful execution of an OPEN statement determines the availability of the file and results in that file being in open mode. A file is available if it is physically present and is recognized by the input-output control system. Table 44 shows the results of opening available and unavailable files. For more information regarding file availability, see the IBM COBOL Programming Guide for your platform.

   Table 44. Availability of a File
   OPENed As	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 the          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

2. The successful execution of the OPEN statement makes the associated record area available to the program; it does not obtain or release the first data record.

3. An OPEN statement must be successfully executed prior to the execution of any of the permissible input-output statements, except a SORT or MERGE statement with the USING or GIVING phrase. Table 45 shows the permissible input-output statements for sequential files. An 'X' indicates that the specified statement can be used with the open mode given at the top of the column.

   Table 45. Permissible Statements for Sequential Files
   Statement	Open Mode
   	Input	Output	I-O	Extend
   READ	X		X
   WRITE		X		X
   REWRITE			X

   
          Table 46 shows the permissible statements for indexed and relative
          files.  An 'X' 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 46. Permissible Statements for Indexed and Relative Files
   File        Access        Mode	Statement	Open Mode
   		Input	Output	I-O	Extend
   Sequential	READ	X		X
   	WRITE		X		X
   	REWRITE			X
   	START	X		X
   	DELETE			X
   Random	READ	X		X
   	WRITE		X	X
   	REWRITE			X
   	START
   	DELETE			X
   Dynamic	READ	X		X
   	WRITE		X	X
   	REWRITE			X
   	START	X		X
   	DELETE			X

   
   
    X      Table 47 shows the permissible input-output statements for line
   
    X     sequential files.  An 'X' indicates that the specified statement can
   
    X     be used with the open mode given at the top of the column.
   
   

   X  Table 47. Permissible Statements for Line Sequential Files (Workstation    X            Only)
   X              X   Statement  X	X                            Open Mode                           X ‘ X      Input
   X ‘ X      Output	X ‘ X       I-O	X ‘ X     Extend
   X     READ	X        X	X	X	X
   X     WRITE	X	X        X	X	X        X
   X    REWRITE	X	X	X	X

4. X A file can be opened for INPUT, OUTPUT, I-O, or EXTEND (sequential and
   X line sequential files only) in the same program. After the first OPEN statement execution for a given file, each subsequent OPEN statement execution must be preceded by a successful CLOSE file statement execution without the REEL or UNIT phrase (for QSAM files only), or the LOCK phrase.

5. If the FILE STATUS clause is specified in the FILE-CONTROL entry, the associated status key is updated when the OPEN statement is executed.

6. If an OPEN statement is issued for a file already in the open status, the EXCEPTION/ERROR procedure (if specified) for this file is executed.

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