It defines the maximum number of fields allowed in one key. If the RMSfile contains fewer secondary keys than the specified number, dtfindi returns a NULL pointer. If the index number passed to dtfindk is zero, dtfindk returns the field numbers that make up the primary key to determine the primary key fields. If the index number passed to dtfindi is zero, dtfindi returns the field names that make up the primary key. If there are no primary key fields, both functions return a NULL pointer.
Any field can have an alias name defined using the alias data type.
The alias field is almost exactly like the original. It also returns the field number of the real field. The dtefldn and dtefld functions are needed when trying to search the key definitions for a particular combination of fields. In particular, it is possible to assign an alias name for any field. This same alias name can be used as the key field name.