A:  EMS uses default session timeout set by Tomcat Server, which is 30 minutes (default value).
There are two ways to change the session timeout value:
1) Open file %CATALINA_HOME%/Conf/web.xml and search:
<session-config>
        <session-timeout>30</session-timeout>
</session-config>
Change "30" to the desired session timeout value.

Note: This will increase the session timeout for all applications (including EMS) that do not have their own session handling.

2) Open file %CATALINA_HOME%\webapps\ems\WEB-INF and search:
  <display-name>ems</display-name>
Just below <display-name>ems</display-name>, place the code lines:
  <session-config>
        <session-timeout>30</session-timeout>
  </session-config>
Change "30" to the desired session timeout value.