Hello,
1) This is possible theoretically, but problematic in a practical way.
2) You could duplicate the alfresco.war / share.war in your Tomcat and call them alfresco2.war and share2.war - when you start your Tomcat, you will be able to access these via the /alfresco2/ and /share2/ URL prefix.
There are a couple of reasons why this is not a good idea to do - the following are the most relevant that come to my mind:
1) Memory consumption - running multiple Alfresco Repository instances on the same Tomcat will linearily increase the memory requirements.
2) Startup times / Restart round-trip duration - running multiple Alfresco instances on the same Tomcat will (most likely) linearily increase the time your server needs for startup / restarts. This can be critical in failure recovery / configuration change situations, where a single Tomcat instance means that you will have to restart ALL Alfresco instances if just one of them is affected.
3) Configuration - Alfresco is configured using <tomcat_root>/shared/classes/alfresco/extension and <tomcat_root>/shared/classes/alfresco/web-extension directories. You can not have configuration for multiple Alfresco instances in that location - they will always share the configuration and run into configuration conflicts (i.e. same ports …)
It is recommended to use different machines for different Alfresco instances. It is also recommended to separate the Share web application from the Repository onto separate Tomcat instances or even machines.
I would NOT recommend attempting to run multiple Alfresco instances in one Tomcat.
Regards
Axel