Upgrade page provides data migration tools for previous versions of Fess.
Download configuration backup files(.fess_basic_config and .fess_user) on Backup page before executing a migration process.
Type /admin/upgrade/ to URL after logging in as admin user. Select a target version and then click button to execute data mingration process.
Fess version from which you want to upgrade.
Create new fess.YYMMDD index and copy documents from old fess index.
Switch fess.search and fess.update aliases after reindexing if enabled.