20.10. Summary

This chapter has taken a long look at the design and implementation of a database library. Although we've kept the library small and simple for presentation purposes, it contains the record locking required to allow concurrent access by multiple processes.

We've also looked at the performance of this library with various numbers of processes using no locking, advisory locking (fine-grained and coarse-grained), and mandatory locking. We saw that advisory locking adds less than 10 percent to the clock time over no locking and that mandatory locking adds another 33 percent to 66 percent over advisory locking.