Controlling Message Size Traced in SNA Server Message Traces (182529)

SUMMARY

Microsoft SNA Server supports dynamic message tracing of various interfaces, including client-server messages and server-host messages, using the snatrace tool. By default, the entire message size is traced to SNA Server trace files (stored in <snaroot>\traces\ with an *.ATF extension, where trace files can be viewed using the SNA Server "tracevwr" tool). However, in some cases, it may be desirable to only trace a limited portion of each message, to reduce the growth and size of the message trace files. SNA Server supports this feature by configuring the "MaxRecordLength" registry entry as described below.

MORE INFORMATION

It is possible to specify the maximum traced message size for SNA Server messages, SNA Server link service messages, and SNA Server Application messages. The message types for which you can specify maximum traced message size are:

Data Link Control messages (between SNA Server and link service)
SNA Server Format messages (between SNA Server and host)
LU6.2 messages (between SNA Server client and SNA Server)
3270 messages (between SNA Server client and SNA Server)

Configuring the MaxRecordLength limits the size of the "element data" traced within each message. For Data Link Control (DLC) messages, the "element data" contains the RH, RU command, and application data. If MaxRecordLength is set to "3," the RH bytes will be traced, but the RU command byte and application data will not be traced. However, the decoded TH, RH, and RU commands, if present, will still be indicated in the header portion of each traced message. The MaxRecordLength parameter does not affect tracing of any other trace fields (such as Windows NT process ID, thread ID, date and time stamp, and so on).

WARNING: Using Registry Editor incorrectly can cause serious problems that may require you to reinstall your operating system. Microsoft cannot guarantee that problems resulting from the incorrect use of Registry Editor can be solved. Use Registry Editor at your own risk.

For information about how to edit the registry, view the "Changing Keys And Values" Help topic in Registry Editor (Regedit.exe) or the "Add and Delete Information in the Registry" and "Edit Registry Data" Help topic in Regedt32.exe. Note that you should back up the registry before you edit it.

When SNA Server message tracing is enabled, you can specify the maximum traced message size by setting the following registry parameter:

   HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\SnaServr
   \Parameters\MaxRecordLength: REG_SZ:  <message size in bytes>

NOTE: The above registry key is one path; it has been wrapped for readability.

This value already exists but is a REG_DWORD type. It must be deleted and re-entered as a REG_SZ. Also, the SNA Server service must be stopped and started for the message size to take effect. This value defaults to 0xFFFF, indicating that you need to trace the entire message.

To enable this setting for SNA Server link services (for example, for DLC messages), configure the following registry value:

   HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\<linkservicename>
   \Parameters\MaxRecordLength: REG_SZ: <message size in bytes>

NOTE: The above registry key is one path; it has been wrapped for readability.

This value already exists but is a REG_DWORD type. It must be deleted and re-entered as a REG_SZ. Also, the SNA Server link service must be stopped and started for the message size to take effect. This value defaults to 0xFFFF, indicating that the entire message should be traced.