If the web server is not performing properly, the log files may provide information. They are located at /var/log/webconsole/. You can increase the log detail level by using smreg:
| smreg add -p debug.trace.level=3 smreg add -p debug.trace.options=tmp | 
The original settings can be restored by:
| smreg add -p debug.trace.level=0 smreg add -p debug.trace.options=m | 
A full dump of the configuration database is triggered by:
| smreg list | 
It is possible that the web server hosting the Desktop Manager may not shut down correctly, leaving its ports in use. This prevents a newly started web server from starting at all. If the smcwebserver start/restart command issues an error messages, or if the Desktop Manager is still accessible even after a smcwebserver stop, or if the newly started server still behaves like the old instance, check if either port 6789 is still in use (netstat -a | grep 6789) or if the web server is still running (ps -ef | grep java). If the one or the other is the case, the according process should be killed and the port 6789 is not in use anymore.