Sequential File Organization
Sequential files organize records according to the sequence in which they are added to a file, by adding each new record at the end. The system retrieves records based upon their relative position in the sequence by using unique record numbers. A sequential file does not contain keys so its records cannot be retrieved by a key path. To select a record based upon field value, APPX must process all records, ignoring those that do not satisfy selection requirements.
In most computer systems, APPX retrieves records from uncompressed, fixed-length record sequential files faster than from indexed files.
A sequential file can contain an unlimited number of records, subject only to available storage space or operating system limitations. You cannot, however, simply delete specific records from this type of file. To eliminate specific records, you must first transfer all records that are to be retained to another file and then scratch the original file.
|