How should do to install two tomcat web instances?

I have one tomcat instance installed and run well. Now I need to copy another one instance from this running one. After I copied it and modified the conf/server.xml, the new instance could not be started.(sudo /xxx/restart_tomcat.sh /xxx/www/mynewInstance) I didn't modify startenv.sh, do I need to modify this file too? catalina log is like this:

 SEVERE: Error listenerStart
Mar 31, 2015 1:02:39 AM org.apache.catalina.core.StandardContext start
SEVERE: Context [] startup failed due to previous errors
Mar 31, 2015 1:02:39 AM org.apache.catalina.loader.WebappClassLoader clearReferencesJdbc
SEVERE: The web application [] registered the JBDC driver [com.mysql.jdbc.Driver] but failed to unregister it when the web application was stopped. To prevent a memory leak, the JDBC Driver has been forcibly unregistered.
Mar 31, 2015 1:02:39 AM org.apache.catalina.loader.WebappClassLoader clearReferencesThreads
SEVERE: The web application [] appears to have started a thread named [Abandoned connection cleanup thread] but has failed to stop it. This is very likely to create a memory leak.
Mar 31, 2015 1:02:39 AM org.apache.catalina.loader.WebappClassLoader clearReferencesThreads
SEVERE: The web application [] appears to have started a thread named [Timer-0] but has failed to stop it. This is very likely to create a memory leak.
Mar 31, 2015 1:02:39 AM org.apache.coyote.http11.Http11Protocol start
INFO: Starting Coyote HTTP/1.1 on http-19033
Mar 31, 2015 1:02:39 AM org.apache.catalina.startup.Catalina start
INFO: Server startup in 2761 ms