The record access modes are sequential, direct by key, and direct by record file address. The direct access modes are possible only with files that reside on disks.
Unlike a file's organization, the record access mode is not a permanent attribute of the file. During the processing of a file, you can switch from one access mode to any other permitted for that file organization. For example, indexed files are often processed by locating a record directly by key, and then using that key's index to sequentially read all the indexed records in ascending order of their key values; this method is sometimes called the indexed- sequential access method (ISAM).