Product Documentation

FairCom ISAM for C

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Standalone Multi-User

There are significant differences in some aspects of FairCom DB between traditional multi-user mode without a server and client/server mode. This chapter discusses the specifics of multi-user mode when not using a FairCom Server.

With traditional multi-user mode the operating system has a great deal of influence on FairCom DB. As discussed in Multi-User Concepts, we use both write locks and read locks. However, not all operating systems supply both. In addition, the manner in which FairCom DB uses write locks may vary from the way that the operating system implements them. Finally, the operating system may limit the number of locks available to your FairCom DB application.

Two types of record locks must be distinguished in FairCom DB: record locks applied to the B-Tree nodes in the index file, and record locks applied to a program’s data records. While the reason for the locks is almost identical, avoiding simultaneous and conflicting updates to the data, there are significant differences in the management of these two classes of locks. FairCom DB automatically takes care of any required node locks, while your application program must control the data record locks.

In This Chapter

Node Locks

Data Record Lock Implementations

Extended Lock Strategy

Dummy Lock File

Exclusive File Opens

EXCLUSIVE File Caching

Multi-User Non-Server Mode Rebuild