This article highlights the detailed steps to self-upgrade Tomcat for TIBCO_HOME for BusinessWorks 5.x. 
Please note Tomcat major version should be the same as the one installed with TRA. It is not allowed to change the major version, e.g. upgrading Tomcat from 9.x to 10.x or 11.x is not allowed.

Steps:
1. Users can download the Apache Tomcat 9.x patch version (latest or choice of their own but that must be in supported range) from https://tomcat.apache.org/download-90.cgi
Alternatively users can go to https://tomcat.apache.org/, in left side panel, click "Tomcat 9" under "Download". 
2. From download page select core and then download the zip package, for example:

3. Unzip the new Tomcat apache-tomcat-9.0.##.zip to folder apache-tomcat-9.0.##.
4. stop all TIBCO components (like tibcoadmin_domainname, hawkagent_domainname, bwengine etc),
5. backup the current Tomcat folder $TPCL_HOME/tomcat/9
6. then copy file bootstrap.jar, commons-daemon.jar and tomcat-juli.jar from apache-tomcat-9.0.##/bin/ to $TPCL_HOME/tomcat/9/bin/, copy folder apache-tomcat-9.0.##/lib to $TPCL_HOME/tomcat/9/lib;
7. If the new tomcat version is tomcat 9.0.90 or higher, users may see error "The request object has been recycled and is no longer associated with this facade" like below when saving .ear files.

To fix this, users need add property discardFacades="false" to tomcat Connector in file $TIBCO_HOME/administrator/domain/domainname/tomcat/conf/server.xml.
 <Connector port="8080" maxHttpHeaderSize="8192" maxThreads="150" minSpareThreads="25" enableLookups="false" acceptCount="100" connectionTimeout="20000" disableUploadTimeout="true" redirectPort="8443" discardFacades="false"/>
8. restart all TIBCO components. 

After this, Users can verify the new Tomcat version through TIBCO Admin GUI, Designer or BW engine runtime.
*** Apache Tomcat 9.x package governed through Apache Software Licensing norms and this is an OPEN source item.
 

Known issue:

1) Users will see error "NoSuchMethodError: org.apache.jasper.runtime.JspRuntimeLibrary.releaseTag" when using tomcat 9.0.96. This is because of API change in tomcat 9.0.96(https://bz.apache.org/bugzilla/show_bug.cgi?id=69333). Please use tomcat version other than 9.0.96.

Please contact TIBCO support if you have any questions.