Starting the trace

To start the DC trace for any terminal in the IMS network, enter one of the /TRACE commands from the master terminal or the z/OS® console.

Specify at least level 3 in the command because buffer contents are usually required for complete diagnosis. If you specify level 4, the trace writes a save area set for certain entries (C00-C12, D05, AER1, and AER2).

For VTAM® terminals:

 /TRACE SET ON NODE P1 LEVEL 1|2|3|4 MODULE DDM|MFS|ALL

For ISC links:

 /TRACE SET ON NODE P1 LEVEL=1|2|3|4 MODULE DDM|MFS|ALL
                       or
 /TRACE SET ON NODE P1 USER P2

For logical LINKs:

 /TRACE SET ON LINK P1,..,Pn|ALL LEVEL 1|2|3|4 MODULE DDM|MFS|ALL

For UNITTYPE:
```
 /TRACE SET ON UNITTYPE P1,..,Pn LEVEL 1|2|3|4 MODULE DDM|MFS|ALL
  UPDATE MSLINK NAME(linkname|linkname*|*) START(TRACE)
```
Note: The type-2 command UPDATE MSLINK NAME(linkname) START(TRACE) uses the same level and module settings that were used the last time the /TRACE SET (ON) LINK command was issued. If a /TRACE SET (ON) LINK command has not been issued since the last cold start, this command defaults to MODULE=ALL and LEVEL=4.
For an XRF environment:
```
 /TRACE SET ON NODE xxx TAKEOVER
 
 /TRACE SET ON LINE xxx TAKEOVER
 
 /TRACE SET ON LINK xxx TAKEOVER

UPDATE MSLINK NAME(linkname) START(TRACE) SET(TKOTRC((Y))
```
Tip:
- The /TRACE SET ON NODExxx TAKEOVER command starts the trace for the specified terminals during takeover only.
- You can enter this command only from the active system in an XRF environment.
- After a terminal has switched successfully, the trace is automatically turned off for that terminal.
- Because this command is recovered across restart and takeover, you need to enter it only once. After a cold start, you must enter the command again.
- Tracing occurs only if the session was active at the time of the takeover.
- If you enter a /TRACE command with and without the TAKEOVER keyword, the last command you entered is in effect.
- You can issue this command for VTAM nodes and MSC links during takeover.
- The /TRACE SET OFF NODE xxx TAKEOVER, /TRACE SET OFF LINE xxx TAKEOVER, /TRACE SET OFF LINK xxx TAKEOVER or UPDATE MSLINK NAME (linkname) STOP(TRACE) SET(TKOTRC(N)) command turns off the trace anytime before takeover.