PRB: NetBIOS Command NCBSEND Gets Return Code Error 0x3C

• Microsoft Win32 Software Development Kit (SDK) for Windows NT, versions 3.1 and 3.5

SYMPTOMS

While opening sessions, you start to get error 0x3C (lock of user area failed) in the NcbSend command call.

CAUSE

An application in Windows NT uses the NcbListen command to accept NetBIOS calls. After a call is received, the application uses the NcbSend command to send data back.

If the computer running Windows NT has 32 megabytes of main memory, an application can request a large number (for example, 128) of sessions, by using the NcbReset command, without difficulty.

However, with only 16 megabytes of main memory, an application can request only a moderate number (for example, 80) of sessions. If more sessions are opened they start to get error 0x3C (lock of user area failed) in the NcbSend command call. The error persists until some of the sessions that are currently open are closed, at which time NcbSend will get a good return status.

STATUS

This behavior is by design. The system stops the process from using so many resources that it jeopardizes the performance of other applications and/or the system itself.