Rebuilding a Corrupt Indexed File

The format of the command line for rebuilding an index is:

rebuild in-file[,out-file]
[-c] [-d] [-e] [-i] [-k] [-n] [-p] [-s] [-v]

The out-file parameter is optional, but recommended, because if you do not specify it, and the Rebuild operation fails, you will lose your original file.

There are a number of reasons why an indexed file becomes corrupt, for example:

• A close operation on an indexed file fails.
• A power surge occurs while the indexed file is open.
• The machine is rebooted or powered off while an indexed file is open.

When a COBOL program attempts to open a corrupt indexed file, the run-time system detects that the file is corrupt and returns an extended file status code.

Rebuild can recover corrupt indexed files for you:

• If the data portion of the file is intact and only the index portion is corrupt, then Rebuild can generate a new index (.idx) file from the data file with no loss of data.
• If the data portion of the file is corrupt then Rebuild can rebuild a complete new indexed file, both data and index portions, but there will be loss of data as Rebuild discards any corrupt data records that it encounters.
  Note: For indexed files that have a separate .idx file (IDXFORMAT4 and IDXFORMAT12), the rebuild process does not remove any incomplete transactional data from the data file. This data is safe to leave in the data file, as it will not be accessible, but if you want to remove it then run a rollback recovery on the file.

In the following example, Rebuild reads the .idx file to get the key information, and creates a new index file, by reading the data file, infile.dat:

rebuild infile.dat

If the data is found to be corrupt, the rebuild process will abort.

In the following example Rebuild reads the input file to get the key information, and creates a new indexed file, by working through the data in physical order, skipping over illegal duplicate records:

rebuild infile.dat, outfile.dat -d -e

If the index file is not present, you must supply information about the key structure using the -k option.