TN3270E Printer Emulators May Have Flow Control Issues

• Microsoft SNA Server, versions 2.11 and 2.11 Service Pack 1

SYMPTOMS

Some TN3270E printer emulators may encounter a dropped session while receiving a large host print job. This problem has been observed with the Attachmate Extra! TN3270E print emulator, although it may occur with other print emulators as well.

CAUSE

The TN3270E protocol specification has no provision for flow control between the server and the client. If the host sends a print job to the emulator using only the exception response protocol (RQE), there is no way for a TN3270E print emulator to indicate any flow control information, used to "throttle back" the rate that the host sends the print job, to the TN3270E server.

RESOLUTION

To resolve this problem, obtain the hotfix mentioned below. In the hotfix, the TN3270E server has been updated to include a new configuration option called "Printer Flow Control." When this option is enabled, the TN3270E server sends all messages to TN3270E printers using definite response protocol (RQD), instead of exception response (RQE). This is implemented as a check box option because this behavior contradicts the TN3270E specification (although it is required for such print emulators to function).

STATUS

Microsoft has confirmed this to be a problem in Microsoft SNA Server versions 2.11 and 2.11 Service Pack 1. This problem was corrected in the latest Microsoft SNA Server 2.11 U.S. Service Pack. For information on obtaining the service pack, query on the following word in the Microsoft Knowledge Base (without the spaces):

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