Sometimes it is necessary to install a new JMD jar file.  JMD jar files are controlled by the VSO folks at the National Solar Observatory. If you are notified by the NSO that there is a new JMD jar file compatible with your current version of Java, you may wish to install it.  To do so:

1.  wget the jar file from the path given by the NSO.
2.  Go to your vso path for JMDs. E.g. /opt/vso/JMD_v1.6.4.0.nohmi/jar
3.  Copy the new jar file into the path for jar files.  There is no need to remove the old one; the JMD will know what to do and will pick up the correct file.
4.  Stop the current jmd process, either as the correct user or through sudo:  {{{sudo /opt/JMD/bin/JMD.sh stop}}}
5.  Make sure there is no other JMD process running.  {{{ps ax |grep java |grep JMD}}}
5.  Delete the current jetty database and its directory.  You will not lose NetDRMS data doing this action.  The JMD will install a new one one on restart.  It is important to delete the entire directory, not just its contents.  
{{{ 
ls /opt/vso/derby/derbyDB/  
sudo rm -rf derbyDB
}}}
6.  Restart the JMD and check the logs:  {{{sudo /opt/JMD/bin/JMD.sh start}}}
7.  Logs should say something like:
{{{
Jun 17, 2014 3:17:52 PM ServerJMD setLogLevel
INFO: Setting new log level to [INFO]
2014-06-17 15:17:52.520:INFO:oejs.Server:jetty-8.y.z-SNAPSHOT
Jun 17, 2014 3:17:52 PM org.vso.jmd.JMD setLogLevel INFO: Setting new log level to [INFO]
Jun 17, 2014 3:17:53 PM org.vso.jmd.JMD init INFO: Starting derby DB /opt/vso/derby/derbyDB at port 31001
Jun 17, 2014 3:17:58 PM org.vso.jmd.JMD init INFO: ij connect string:[connect 'jdbc:derby://localhost:31001//opt/vso/derby/derbyDB';] on try 1
Jun 17, 2014 3:18:01 PM org.vso.jmd.HouseKeepingThread run INFO: HouseKeepingThread: HouseKeeping heart beat ...
Jun 17, 2014 3:18:01 PM org.vso.jmd.HouseKeepingThread run INFO: Compacting the derby Database
Jun 17, 2014 3:18:01 PM org.vso.jmd.HouseKeepingThread run INFO: Derby Database Compacting Done
2014-06-17 15:18:01.530:INFO:oejs.NCSARequestLog:Opened /var/log/jmd/jetty-2014_06_17.request.log
2014-06-17 15:18:01.571:INFO:oejs.AbstractConnector:Started SelectChannelConnector@0.0.0.0:8080
}}}
with no errors about Jetty not restarting.