In Chapter 2 we presented an architecture for a DBMS. Figure 20.3 represents an extract
from Figure 2.8 identifying four high-level database modules that handle transactions,
concurrency control, and recovery. The transaction manager coordinates transactions on
behalf of application programs. It communicates with the scheduler, the module respons-ible for implementing a particular strategy for concurrency control. The scheduler is
sometimes referred to as the lock manager if the concurrency control protocol is locking-based.