You can connect to multiple instances of Essbase simultaneously from the Planning application by specifying the port number:
When creating a Planning application with the Classic Application wizard or in Performance Management Architect (repeat for every data source name).
As the value for the property ESS_SERVER in the HSPSYS_DATASOURCE database table.
For instructions on installing multiple instances of Essbase on the same computer, see the Oracle Essbase Database Administrator's Online Help.