The NetWare Btrieve programs function as if they were a subroutine of your application program. NetWare Btrieve supports the following two methods for accessing BSERVER:
• A workstation application can access BSERVER via the BREQUEST program.
• A workstation application can call a VAP, which then communicates with BSERVER via BROUTER.
The following sections describe the two methods of access.
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Introduction to Btrieve
ACCESS TO BSERVER VIA BREQUEST
The following steps illustrate the flow of control when a workstation application accesses BSERVER via the BREQUEST program loaded at the workstation.
• Your application program issues a Btrieve request in the form of a function call. The actual call is implemented slightly differently in different languages. For simplicity, this manual will refer to a Btrieve call as a function call, or Btrieve call.)
• A short interface routine included in your application program packages the call parameters in a block of memory, saves the source stack, and makes the call to BREQUEST.
• BREQUEST packages the request into a network message, determines which server should receive the request, and routes the message to the BSERVER program resident at that server.
• BSERVER receives the network message, validates the parameters, and then executes the instruction. Depending on the nature of the
instruction, this could involve a memory-only operation or an I/O operation to a system storage device. BSERVER then returns the results of the operation to the BREQUEST program at the workstation.
• BREQUEST returns the appropriate data and status code to the
parameter variables or structures in your application's memory, restores the source stack, and returns control to your program.
If an application at a workstation makes Btrieve requests to both a local (nonshared) drive and a network (shared) drive, a copy of either Btrieve Single User or Btrieve for DOS 3.1 Networks must be loaded at that workstation, as well as BREQUEST. BREQUEST determines whether the request should be transferred to the local Btrieve servicing the non shared files or to the BSERVER program that services the shared files at the server.
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Figure 1.2 illustrates a sample configuration for a simple Novell network
Network Configuration Using BSERVER.VAP (Note that Workstation 2 accessea both shared and local files.)
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Figure 1.3 illustrates a network with a multiple file server configuration. In this diagram, file servers A and B service the shared files on the network.
Notice that all stations on the network can make Btrieve requests to either file server. The BREQUEST programs loaded at each workstation route the requests to the appropriate file server. Proper identification of the file servers and volumes is essential to the correct functioning of the system.
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NetWare Shell NetWare Shell
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BREOUEST BREOUEST:=J C
Btrieve Btrieve
Application Application
Workstation 1 Workstation 2
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Local1.-.
DOS3.x Disk
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DOS3.xNetWare Shell NetWare Shell
~ BREOUEST
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Btrieve RecordBtrieve
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ManagerApplication BREQUEST
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Workstation 3 Application Btrieve
Workstation 4
Network with Multiple File Servers
(Notice that BREQUEST loaded at each workstation can access each Btrieve file server.
Workstation 4 is configured to access both shared and local Btrleve files.)
If you are using multiple file servers or an internetwork, all of the file servers do not have to be on line when you start BREQUEST at the workstations.
BREQUEST recognizes new file servers or drives when you attach to a new file server or change your network drive mapping.
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ACCESS TO BSERVER VIA BROUTER NOTE:
If you are not developing a Value-Added Process (V AP) that accesses NetWare Btrieve, you may skip this section.
The following steps illustrate the flow of control when a workstation application calls a V AP which then accesses BSERVER via the BROUTER program.
• A workstation application issues a request to a VAP. The request may be formatted as a Btrieve call or in the form required by the V AP.
• An interface routine included in the application program packages the request into a network message, determines which server should receive the request, and routes the message to the V AP resident at that server.
• The V AP receives the network message, validates the parameters, and packages the call parameters as a Btrieve request in a block of memory.
It then stores the client ID in the AX register and executes the 7B interrupt.
• BROUTER receives the Btrieve request, stores information about the origin of the call, and calls the copy of BSERVER active at the server where the file is stored.
• BSERVER processes the request and returns the results of the operation to BROUTER.
• BROUTER returns the appropriate data and status code to the parameter variables or structures in the V AP's memory and returns control to the VAP.
• The V AP returns the appropriate information to the application at the workstation.
If a workstation application makes Btrieve requests to a local (nonshared) drive and also to a V AP that calls Btrieve, a copy of either Btrieve Single User or Btrieve for DOS 3.1 Networks must be loaded at that workstation.
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Introduction to Btrieve
Figure 1.4 illustrates the flow of control when a V AP accesses Btrieve files using NetWare Btrieve.
1. An application at a workstatio issues a request to VAP1
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2. The interface for VAP1 sends the request to the server
3. VAP1 packages a request and executes Int 7B
4. BROUTER receives the Btrieve call and passes it to BSERVER
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Using Another YAP with BSERVER
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