You may see the following event logged in the application event log after enabling the 3270 Messages trace option for  TN3270 in the SNA Trace Utility (snatrace.exe):

Event ID: 903
Type: Warning
Source: TN3270 Server
Description:
Windows API SetCurrentDirectory failed with error code 5L (Access is denied.) in function FirstTimeProcess.

This occurs when the user account that the TN3270 service runs under does not have proper permissions to the Host Integration Server traces folder (e.g. C:\Program Files\Microsoft Host Integration Server 2006\traces).

By default, the following permissions are granted to the HIS traces folder when using HIS 2006:

Group or user names

Permissions

Administrators Full Control
HIS Runtime Users Read, Write

Note: If the Allow HIS Administrators to perform tracing option is enabled under the “Tracing Global Properties” tab in the SNA Trace Utility, the HIS Administrators group will be granted Full Control permissions to the HIS traces folder as well.

The HIS Runtime Users group includes the user account (by default) that the Host Integration Server services run under. You could add specific permissions to the HIS service account to correct this problem, but a better option is to grant the needed permissions to the HIS Runtime Users group.

If you grant the HIS Runtime Users group the Traverse Folder / Execute File permission to the HIS traces folder, the Event 903 warning will not be logged by the TN3270 service when enabling the 3270 Messages trace option.

When the 3270 Messages trace option is enabled for TN3270, the TN3270 service attempts to create the following trace files:

- TN3MSG1.ATF
- TN3MSG2.ATF
- tn3_00.trc

The TN3MSG1.ATF and TN3MSG2.ATF trace files are created successfully with the default permissions that are granted to the HIS traces folder. The tn3_00.trc trace file is not created when the HIS Runtime Users group does not have the Traverse Folder / Execute File permission.

The tn3_00.trc trace file captures the TN3270 data that the TN3270 service sends to and receives from TN3270 emulators.