function IsSequenced: Boolean; override;
virtual bool __fastcall IsSequenced();
IsSequenced indicates whether sequence numbers are available for database records.
Call IsSequenced to determine whether database records can be located by sequence numbers. When IsSequenced is true, the dataset can navigate directly to a specific record by setting the RecNo property. If IsSequenced is false, the only way to navigate to a specific record is to start at the beginning and count records.