Actually, AppleTalk (typically) would not be the limiting factor in a scenario
of this nature. Under the Macintosh OS, there is a default limit to the number
of files that you can have open at one time. If you have less than 1MB of
memory, this default is 10; if you have 1MB or more, the default is 40. This
limit applies to local volumes as well as network-based volumes. Most
databases that are network-aware use AppleTalk Filing Protocol (AFP) calls to
access the files on a server. Files opened via AFP calls, just like files
opened via the native filing interface, are counted in the operating system
limit.
You can modify the limit of the number of open files by modifying the boot
blocks on your startup volume, but this is not recommended and is (typically)
not necessary. For example, 4th Dimension opens a number of files from a
server when it is running in multi-user mode, but you still have plenty of
"room" to operate within the open file limit.
If you are concerned by the number of files that are open on the server and not
the workstation, remember that one file opened by multiple workstations counts
as only one open file on the server. On a server with 2MB of memory or more,
the maximum number of files that can be opened at one time is 160. If you have
1MB of memory, the maximum number of opened files is 60.
The number of files that can be opened on other servers (like a Novell server)
depends on that manufacturer's implementation of an AFP-based server, because
there is no specific limit in AFP.