Upgrading one or both of the backend databases for SCH 3.x (relational database and timeseries database) has no effect on SCH itself assuming that you are upgrading to a supported version of the database. You will need to either bring down SCH during the upgrade, or put the database into read-only mode, and of course take a backup of the database before beginning the upgrade.
In a scenario where a subsequent rollback of the database to the backed-up version is contemplated, be aware that there will be some data loss, even if there were no new jobs created or other changes made (code freeze). Some of this data includes, but is not limited to:
- Any clean up of the DB
- Writing to InfluxDB
- Writing to the PostgreSQL Timseries DB (job metrics that don’t go to InfluxDB but to the SQL DB)
- Updating jobs statuses
- Running scheduler tasks
These data would need to be manually reconstructed from the upgraded database and backported to the rolled-back database.
If you have any additional questions, please don’t hesitate to contact StreamSets Support.