I checked and it says 255 concurrent users. But through code I cannot open more than 64 connections.
That may be a limit on your client, rather than the data file. Every connection, after all, requires client resources (memory/processing/bandwidth) to support it.
What the spec says and your practical limits are two entirely separate things.
At my work site, we use both Windows and Netware file servers, and I've had trouble with databases over 50 MB and 3 or so users getting corrupted databases fairly regularly. That's just the nature of a file-based database like Access. Also, networks that are subject to interruption or long delays (Wireless, anyone...) create an environment that is hazardous to Access databases.
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