A Cobol program reads a record from a first flat file and compares it to the first record on a second flat file. However, because the first record from the first flat file does not match any records on the second flat file, the Cobol program goes into an infinite loop. How do I fix it?
Smells like a logic error somewhere in the program. Hard to say what that might be. But I do have a few ideas...
Possible causes of an infinite loop:
End of file is sometimes determined by testing the File Status after each I/O operation. File Status is an optional 2 character data item associated with the file being read/written. It is specified in the FILE-CONTROL paragraph of your program. For example:
SELECT file-name ASSIGN TO dd-name FILE STATUS fstatus
file-name is the name you refer to in OPEN/READ/WRITE/CLOSE statements.
is the external file name (the DDNAME from your JCL).
fstatus is a two character data item declared
The File Status is set on every file I/O operation. For example:
fstatus to end-of-file if there were no more records to read. Note that the File Status
variable is not actually referenced on the
READ, but it is set.
File Status values are two characters and are defined in the ISO COBOL standard, they should be the same for all COBOL implementations. The exception being File Status values where the first character is a '9', these are implementation dependant. Here is a link to the IBM Enterprise COBOL File Status values The value for end-of-file is: '10' - which should be the same for all COBOL implementations.
It is my guess that your program has a File Status for each of the input files, but is not checking it or reacting to it appropriately. For example, your program may only check for end-of-file but not other conditions:
IF fstatus = '10'
The problem with this approach is that it treats normal returns (fstatus = '00') and all non-end-of-file error conditions as if the READ was successful. Better to have something like:
There is an imperative form of the
READ statement that specifies what to do when the end of file
is reached. It goes something like:
READ file-name AT END PERFORM END-OF-FILE-LOGIC END-READ
Again, if a File Status was specified in the FILE-CONTROL section for
file-name and a non-end-of-file
error occurred, your program would attempt to continue with 'normal' logic - exactly the wrong thing to be