Oracle Database 12c Release 2 has been released on the Oracle Database Cloud. We are going through some interesting features of this new 12.2 release, such as things that have been glossed over in other reports.
For Database upgrades, there are improvements in the automation components of the upgrade, so as to reduce the upgrade effort. The Pre-Upgrade Information Tool has been enhanced, there is more clarity and consistency and the fix up routines have been expanded and enhanced – these can now self-validate to detect cases where the fix up is no longer needed. Also, the Pre-Upgrade Information Tool is available as a single .jar file so that you can easily move the tool between systems.
Another interesting, useful addition is that there is a new -T option for the parallel upgrade utility called via the catctl.pl script. This can be used to automatically set user tablespaces to read-only during an upgrade, and later on to read/write after the upgrade is complete. If any issue is encountered during the upgrade, this can be used as a way to fallback.
The steps in this case would be to first copy the system tablespaces to local disks as a fallback copy, then use the -T option in the upgrade to set user tablespaces to read-only, while the upgrade is progressing. If the upgrade has any issue, and you want to fall back to the original database, then you can restore the copies of the system tablespaces and quickly restart the database, and it will be opened in the original Oracle Home.
Additionally, this new functionality is also supported by the Database Upgrade Assistant (DBUA) in Oracle Database 12.2, if you are using the DBUA tool for the upgrade.