I used this tool when i was migrating from V8.0 to V8.5.5.  This guide is a must read for WPS Administrators.

This guide provides a comprehensive approach to performing staging to production using Portal Application Archive (PAA) in IBM WebSphere Portal 8.5.

Introduction
Preparing the source environment
Preparing the target environment
Creating the initial release
Deploying the initial release
Updates with syndication
Updates with ReleaseBuilder
Known Problems
Acknowledgments
References
Change History

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WebSphere Portal