 | Programmer's Guide (9.1 revision 1) |  |
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File sharing is the ability of multiple clients to operate on the same file. Versions of the MicroKernel prior to Pervasive.SQL 2000 supported multiple clients accessing the same file simultaneously. This mechanism was referred to as Multi Engine File Sharing (MEFS), and it had many limitations including limited use of cache and increased network traffic. In Pervasive.SQL 2000 and later releases, the Workgroup engine replaced MEFS. The Workgroup design only permits one database engine to access a data file at one time, but allows other clients to share this data by using another engine as a gateway to that data. The Pervasive MicroKernel also supports client/server mode.
See Advanced Operations Guide for more information about Workgroup engines.
Workgroup engines can access local database files and send requests to remote server engines.
Workgroup engines are local engines that can also act as the gateway for database requests from other machines.
Server-based engines use a client/server configuration using a single MicroKernel running at a Linux, NetWare, or Windows NT server handling the I/O requests from multiple clients.
Two client workstations are local clients relative to each other if they run under the same engine. Similarly, two clients are remote clients relative to each other if they run under different engines. Based on these definitions, a client can be both local relative to some clients (those running under the same engine) and remote relative to other clients (those running under different engines) at the same time.
Note
Clients that run on different workstations but use the same server-based engine are local clients, because they use the same engine. Whenever a distinction is made between local and remote clients, only the information relevant to local clients is applicable for server-based engines.
If your application uses the BTRVID function to define and manage multiple clients within the same application, such clients are considered local clients.
DOS developers: In multi-tasking DOS environments or in Windows when using DOS boxes, Btrieve for DOS must be loaded in each task's address space. Therefore, such clients are considered remote clients.
When you open a file in SEFS mode, only local clients can share the file. The engine's functionality is available without restrictions to local clients.
Only server-based engines perform deadlock detection for remote clients.
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