I have tried to save the Orbeon forms in Postgres DB. I created data bases persistence layer but still forms are stored in
I'm not sure what you mean by "created context in the Server.xml".
In tomcat's server.xml you should have a datasource defined. For example:
Then in tomcat's context.xml you should have a ResourceLink for the datasource:
properties-local.xml should be either in webapps/orbeon/WEB-INF/resources/config or in an external directory you have defined in tomcat's context.xml, for example:
In that case the properties-local.xml should be here: C:\orbeon_resources\properties-local.xml. See Storing configurations outside of the Orbeon Forms war file.
Also, make sure you have performed the Orbeon Forms setup. That is general database configuration, not specific to postgresql or any other database implementation. The examples they give are for oracle but you can just replace oracle with postgresql.