Sometimes when a user accesses a file migrated from Acucobol or RM/COBOL to either Jisam or c-tree file systems, the order of the alternate keys can change from the previous COBOL dialect used.
In these cases or even when we created a brand new file, it's important to use the appropriate compiler options for handling alternate keys.

When migrating from ACU to Jisam or c-tree or accessing an original file by using Visionj file connector, make sure you compile the program with '-cko' option.
This compiler option lists keys in offset order. Without this option keys are listed following the order they're declared in the FILE-CONTROL paragraph.

There is a similar compiler option, '-crko', specific to RM/COBOL data files. Just like '-cko', without this option keys are listed following the order they're declared in the FILE-CONTROL paragraph. But '-crko' handles split keys with multiple segments differently.
The -crko will evaluate all segments of the key for the offset, while -cko only evaluates the first segment for the offset.

Note that the -cko and -crko options change the order in which keys are registered in the physical file (you can verify this with file management utilities such as jutil and ctutil). As a consequence, this option affects XML/ISS dictionaries as well as the I$IO and file interfaces where keys are indicated by ordinal number.

Here's an example. The attached program, create-file.cbl, will create a file called "songs" with three alternae keys. The keys are declared in the file-control paragraph this way:

    select songs assign to "songs"
           organization is indexed
           access is dynamic
           record key is sr-key
           alternate record key is key2 = sr-artist sr-genre sr-album duplicates
           alternate record key is key3 = sr-artist sr-album sr-genre duplicates
           alternate record key is sr-title duplicates
           file status is file-status.

    fd songs.
    01 songs-record.
       05 sr-key.
          10 sr-id          pic 9(5).
       05 sr-data.
          10 sr-title       pic x(30).
          10 sr-length      pic x(5).
          10 sr-artist      pic x(20).
          10 sr-album       pic x(30).
          10 sr-genre       pic x(15).
          10 sr-label       pic x(30).
          10 sr-year        pic 9(4).
          10 sr-authors     occurs 5.
             15 sr-author   pic x(20). 

• When compiled without any option, the order of the keys would be: sr-key, key2, key3, sr-title.
• With -cko, the order is changed to follow the order of the fields in the FD: sr-key, sr-title, key2, key3.
• With -crko, the order is changed to follow the order of the fields in the FD also for segments: sr-key, sr-title, key2, key2.

To see this in detail, compile the program with -cko or -crko and without any option, run it to create the file songs, and look at the file with jutil, using the -x option to display the offsets:

   jutil -info songs -x 

Key  Dups Segments
  1    N      1      Seg.   Offset    Size
                      1         0       5
  2    Y      3      Seg.   Offset    Size
                      1        40      20
                      2        90      15
                      3        60      30
  3    Y      3      Seg.   Offset    Size
                      1        40      20
                      2        60      30
                      3        90      15
  4    Y      1      Seg.   Offset    Size
                      1         5      30 

Key  Dups Segments
  1    N      1      Seg.   Offset    Size
                      1         0       5
  2    Y      1      Seg.   Offset    Size
                      1         5      30
  3    Y      3      Seg.   Offset    Size
                      1        40      20
                      2        90      15
                      3        60      30
  4    Y      3      Seg.   Offset    Size
                      1        40      20
                      2        60      30
                      3        90      15

Key  Dups Segments
  1    N      1      Seg.   Offset    Size
                      1         0       5
  2    Y      1      Seg.   Offset    Size
                      1         5      30
  3    Y      3      Seg.   Offset    Size
                      1        40      20
                      2        60      30
                      3        90      15
  4    Y      3      Seg.   Offset    Size
                      1        40      20
                      2        90      15
                      3        60      30

• createfile.cbl

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