File Access Method

The File Definition form describes how records are stored in the RMSfile. The first field, File Access Method, describes the organization of the records in the RMSfile. The choices allowed are: indexed, hashed, and sequential.

In hashed files, each new record is placed at the record number calculated by the hash function. The record is then stored in that calculated slot. This method should be used for RMSfiles that are static in nature and in which few additions and deletions of records need to be made.

In sequential files, each new record is placed at the end of the file in the first unoccupied slot. Sequential files are not typically used for data entry files but are used as temporary work files for programs.

Indexed files are often referred to as ISAM (indexed sequential access method) files. Each new record is placed at the end of the file in the first unoccupied slot. The value of the record's primary key and the record's location are then added to the RMS index file. In most cases, indexed files are sufficient for data entry files and are the normal choice when creating RMS definition files.

If the File Access Method field is blank when the RETURN key is pressed, indexed is automatically entered in the field, since it is the default value for this field. If the field is non-blank when you exit the field, the field value must be an abbreviation of one of the valid File Access Methods. For example, h, ha, has, hash, hashe, and hashed are all abbreviations of hashed, but hndexed does not match any File Access Method. The full File Access Method is displayed after you exit the field.