If both Smart IT and DWP are on the SAME server Smart IT 18.08, Smart IT 19.02 stops working after upgrading DWP to 19.02.

You will run into below errors in the tomcat logs

Tomcat log:
 
07-Mar-2019 07:57:43.346 SEVERE [localhost-startStop-1] org.apache.catalina.core.StandardContext.startInternal One or more Filters failed to start. Full details will be found in the appropriate container log file
07-Mar-2019 07:57:43.346 SEVERE [localhost-startStop-1] org.apache.catalina.core.StandardContext.startInternal Context [/smartit] startup failed due to previous errors

07-Mar-2019 07:57:43.643 WARNING [localhost-startStop-1] org.apache.catalina.loader.WebappClassLoaderBase.clearReferencesThreads The web application [smartit] appears to have started a thread named [logback-1] but has failed to stop it. This is very likely to create a memory leak. Stack trace of thread:
sun.misc.Unsafe.park(Native Method)
 
07-Mar-2019 07:57:42.830 SEVERE [localhost-startStop-1] org.apache.tomcat.util.descriptor.web.SecurityConstraint.findUncoveredHttpMethods For security constraints with URL pattern [/*] only the HTTP methods [TRACE OPTIONS] are covered. All other methods are uncovered.

07-Mar-2019 07:57:43.065 SEVERE [localhost-startStop-1] org.apache.catalina.core.StandardContext.filterStart Exception starting filter Agent
java.lang.NoClassDefFoundError: io/jsonwebtoken/ExpiredJwtException
                at com.bmc.rsso.agent.RSSOAgent.initHelper(RSSOAgent.java:198)
                at com.bmc.rsso.agent.RSSOAgent.<init>(RSSOAgent.java:118)
                at com.bmc.rsso.agent.RSSOAgent.<init>(RSSOAgent.java:68)
                at com.bmc.rsso.agent.RSSOAgent$RSSOAgentHolder.<clinit>(RSSOAgent.java:776)
                at com.bmc.rsso.agent.RSSOAgent.getInstance(RSSOAgent.java:153)
                at com.bmc.rsso.agent.RSSOFilter.init(RSSOFilter.java:54)
                at com.bmc.atrium.sso.agents.web.SSOFilter.init(SSOFilter.java:47)
                at com.bmc.bsm.myit.filter.SSOFilterWrapper.init(SSOFilterWrapper.java:38)
 

This knowledge article may contain information that does not apply to version 21.05 or later which runs in a container environment. Please refer to Article Number 000385088 for more information about troubleshooting BMC products in containers.

To workaround this issue, please navigate to the "Tomcat\external-conf\lib" directory and replace all rsso jar files with 18.11 rsso jar files (Please find them attached in article ) and restart Tomcat.

Note: It is NOT recommended to have both DWP and Smart IT on the same server in production.
Please, install both applications on different servers, if that is not possible, then use different Tomcats. That is documented below:
https://docs.bmc.com/docs/display/dwpadv1805/Upgrading+BMC+Digital+Workplace  


Another scenario where we observed that the Smart IT with RSSO keeps spinning.
1. Compare the file size of the rsso jars with working environment {In 1808 it worked so compared the file size of the jar files}

File size of the smartit 19_02 installer
[root@localhost logs]# ls -ltr /tmp/rss*
-rwxr-xr-x 1 root   root     222363 Jul 12 09:53 /tmp/rsso-agent-all-RSSO_19.02.00-RC4.jar
-rwxr-xr-x 1 root   root       5578 Jul 12 09:53 /tmp/rsso-client-impl-RSSO_19.02.00-RC4.jar
-rwxr-xr-x 1 root   root       8632 Jul 12 09:53 /tmp/rsso-sdk-atsso-RSSO_19.02.00-RC4.jar

File size of the smartit 18_08 installer
[root@localhost tomcat]# ls -l /apps/tomcat/tomcat8.5_smartit/external-conf/lib/
-rwxr-xr-x 1 root root 192452 Jul 12 10:15 rsso-agent-all.jar
-rwxr-xr-x 1 root root   5578 Jul 12 10:15 rsso-client-impl.jar
-rwxr-xr-x 1 root root   8632 Jul 12 10:15 rsso-sdk-atsso.jar

Replaced the jars of 1808 version in 1902.