Every parameter has a name and a number associated with it. Either the name or the number can be used to specify the parameter. If the parameter is from the current database, then the current database name is used by default. The database name need only be specified when two or more base tables are accessed simultaneously. These entry numbers are not unique and they change if the current index is changed, or if the selection of entries is changed.
Samples allow pointers to selected records to be saved in a file for later recall.
The record numbers that make up a sample are stored in a file which is ordered on the value of a particular parameter. The pointers contained in the file are then used to access entries in that order. The index file is used both to search rapidly for all entries corresponding to a range of values, and to list the selected sample in the order of a particular parameter value. All indexes are in descending order. The number of disk reads required to perform the search determines the speed at which the records are found.