Do we have any process for migration of OneStream application from environment to other

I'm assuming you're on Cloud versus On-Prem. 

Use OS Service Portal Cloud Customer that your company is already registered to use. Under Catalog, select "Application Copy" and fill the form (source environment/application to target environment/application). The support team will then copy the underlying app database across environments. It's usually done within a 1/2 hour.

If you're OS environments are On-Prem, your SQL DBA should be able to copy the app database across SQL instances.