1) The document provides steps for performing a manual rolling upgrade of an Oracle database from a single-instance configuration to Real Application Clusters (RAC) with zero downtime.
2) It outlines taking backups of the production database, control files, and redo logs before upgrading the database software and migrating to a RAC configuration.
3) The rolling upgrade process involves restoring the backups, recovering the database through archived redo logs, and repeating the backup and recovery steps incrementally until the database can be opened in RAC mode after upgrading the catalog.