There is probably a more precise error message in your ccm.log or in
one of the two Websphere logs SystemOut.log or native_stderr.log, which
points out preciselly why this CRJAZ1579E error occurs for "The DDL
Provider (DB2) failed to load.". For Tomcat errors may be in Catalina.out.

To troubleshoot this issue you should:
1. Look at ccm.log and the other logs (SystemOut.log,
native_stderr.log, catalina.out) to see if there is a specific error message there.
Send the logs to support in a PMR if you want assistance in analyzing those.

2. Most of the same options for JDBC generally need to be applied to
both CCM and JTS, depending on your deployment. The interactive install
guide should have the exact steps so you can trace over those steps
again for CCM and that may help.

3. Also, if you add a Java option -verbose:class to the custom options
for the JVM in Websphere, SystemOut.log will list all classes that are
being loaded from what files. This can help troubleshoot class loading
issues.

4. If this is not a class loader issue, the "repotools-ccm -clean"
command could help refresh all the files which could cause the issue.
So you can:
   1. Stop the server
   2. Run this from a command line in the CCM installation directory:
repotools-ccm -clean
   3. Start the server
   4. Try the jts/setup again.