ERROR main org.apache.catalina.core.ContainerBase.[Catalina] - Exception looking up UserDatabase under key UserDatabase
 javax.naming.NamingException: /app/tibco/administrator/domain/prodtib/tomcat/conf/tomcat-users.xml
    at org.apache.naming.NamingContext.lookup(NamingContext.java:805)
    at org.apache.naming.NamingContext.lookup(NamingContext.java:153)
    at org.apache.catalina.realm.UserDatabaseRealm.start(UserDatabaseRealm.java:253)
    at org.apache.catalina.core.ContainerBase.start(ContainerBase.java:1006)
    at org.apache.catalina.core.StandardEngine.start(StandardEngine.java:443)
    at org.apache.catalina.core.StandardService.start(StandardService.java:448)
    at org.apache.catalina.core.StandardServer.start(StandardServer.java:700)
    at org.apache.catalina.startup.Catalina.start(Catalina.java:552)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
    at java.lang.reflect.Method.invoke(Method.java:597)
    at org.apache.catalina.startup.Bootstrap.start(Bootstrap.java:295)
    at org.apache.catalina.startup.Bootstrap.main(Bootstrap.java:433)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
    at java.lang.reflect.Method.invoke(Method.java:597)
    at com.tibco.administrator.startup.AdminWrapper.<init>(AdminWrapper.java:208)

    at com.tibco.administrator.startup.AdminWrapper.main(AdminWrapper.java:75)

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This issue is seen when the tomcat-users.xml is missing or when there are permission issues.

1). Check if the tomcat-users.xml file with content is present in the <TIBCO HOME>/administrator/domain/<DOMAIN NAME>/tomcat/conf folder. If the file is empty, or not present, copy the file from another domain and modify the file. The tomcat-users.xml file below is a sample.

--------------------tomcat-users.xml----------------------

<?xml version="1.0" encoding="UTF-8"?>
<!--
  NOTE:  By default, no user is included in the "manager" role required
  to operate the "/manager" web application.  If you wish to use this app,
  you must define such a user - the username and password are arbitrary.
-->
<tomcat-users>
    <user name="admin" password="xQh@nDhaCnpSJgH9r9hadFpRJ@DvyUxQEFdDurje" roles="manager-script"/>
</tomcat-users>

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2). Check if the user under which the domain administrator is running has the necessary permission on Tomcat directory and its sub folders. Specifically, check the permissions on the tomcat-users.xml file.