Abstract: A system and method allows a host computer to operate as a server in a client-server arrangement in response to requests from client computer systems. The system and computer program product performs reads, reads for update, update and deletes on some or all records in a file, depending on the type of file. Record or file locking is provided when applicable. Security is provided at the file level. Abnormal ends of communication with the client computer system are detected to allow resources and record or file locks to be freed in such event. A counter is incremented at the time a client computer system logs into the host computer system to enforce limits on the number of concurrent users, and ordinary log off as well as abnormal ends of communication decrement the counter to maintain its accuracy.