A heterogeneous distributed database system (HDDBS) is a system which integrates preexisting databases to support global applications accessing more than one database. An outline of approaches to concurrency control in HDDBSs is presented. The top-down approach emerges as a viable paradigm for ensuring the proper concurrent execution of global transactions in an HDDBS. The primary contributions of this work are the general schemes for local concurrency control with prespecified global serialization orders. Two approaches are outlined. The one is intended for performance enhancement but violates design autonomy, while the other does not violate local autonomy at the cost of generality (it does not apply to all local concurrency control protocols). This study is intended as a guide to concurrency control in this new environment.