VSAM file status keys can help you determine whether routine errors are due to the logic of your routine or are I/O errors occurring on the storage media. To use file status keys as a debugging aid, include a test after each I/O statement to check for a value other than 0 in the file status key. If the value is other than 0, you can expect to receive an error message. You can use a nonzero value to indicate how the I/O procedures in the routine were coded. You can also include procedures to correct the error based on the file status key value.