The following are required to upgrade a DB system:

• The DB system must use Oracle Linux 6 (OL6) or Oracle Linux 7 (OL7).
• Oracle recommends having a complete standalone backup of the database.

For DB system upgrades, note the following:

• You could upgrade any existing DB system OS from OL6 or OL7 to OL8 and GI to 19c.
• When you are on OL7, only the OS will be upgraded to OL8. The GI will not be upgraded.
• Databases earlier than 19.21 or 21.12 will be launched with OL7, which includes restoring a backup or a Data Guard standby creation. Databases from 19.21 or 21.12 onwards will always be provisioned with OL8. The OS version of a new DB system (restore or Data Guard) will therefore depend on the database version, regardless of the OS of the source DB system. If you require OL7 with the latest (e.g., 19.21 or 21.12) database update, you need to launch with an older DB version (e.g., 19.20 or 21.11) and update to the latest version.
• DB system upgrades involve some downtime (even on RAC DB systems). Plan and schedule your upgrade accordingly.
• Oracle recommends disabling the automatic backups before executing the upgrade.
  Note
  
  The upgrade process will itself disable and re-enable the automatic backup. However, Oracle recommends you do it after careful consideration.
• The upgrade process creates a new compute instance and clones the data disks.
• The private IP addresses and hostnames are carried over to the upgraded DB system.
• The ephemeral public IP addresses are not carried over and will change in the upgraded DB system.
• Oracle recommends not to launch any new instances within the subnet of the DB system. There is a short interval when the private IP addresses and hostnames are "free" during the upgrade process. During this interval, launching any new instance could reserve the "free" IP addresses and block the upgrade process.
  Note
  
  If any instances block the upgrade process, the upgrade process will automatically continue after you terminate the blocking instance.
• All changes to the OS will be removed and are not carried over to the new OS.
• All changes to Clusterware other than the database and services will be removed and are not carried over to the new GI stack.
• For databases with a Data Guard association, the upgrade is only allowed on the standby site. It ensures no re-instantiation is required as the standby could be ahead of the primary in case of rollback.
• Oracle recommends switching the Data Guard association to "Maximum Performance" before the upgrade, as otherwise, the primary will run into NET_TIMEOUT, and a reset of the configuration is required afterward. After the upgrade, if required, you can turn it to "Maximum Availability".

You can roll forward upgrades that did not complete successfully for the following reasons using the Oracle support team.

• Database registration failed.
• Database startup failed even after a successful upgrade of OS and GI.

You can roll back upgrades that did not complete successfully. A rollback resets your DB system to the state before the upgrade. All changes to the DB system made during and after the upgrade will be lost.

After the rollback, you can try upgrading the DB system again after finding and fixing the cause of the earlier upgrade failure.

After a successful upgrade, note the following:

• Check that automatic backup is enabled for the database if you disabled them before upgrading.
• The upgrade exchanges the boot volume. So all customization of the OS will be removed (and have to be reapplied by the customer).
• As the GI stack is reinstalled, you have to reapply all Clusterware customizations (like services, additional virtual IPs, etc.).
• Check that automatic backup is enabled for the database if you had disabled them before upgrading.

Perform the following steps to upgrade the operating system of a DB system.

1. Open the navigation menu. Select Oracle Database, then select Oracle Base Database Service.
2. Select your Compartment. A list of DB systems is displayed.
3. In the list of DB systems, click the name of the DB system you want to upgrade. Details of the DB system you selected are displayed.
4. In the DB system information tab, under Version, click the View link beside the Upgrades available field.
5. Under DB system, under OS updates, review the list of available OS upgrades for the DB system.
6. Click the Actions menu for the upgrade you are interested in, and then click one of the following actions:
   • Run Precheck: Check for any prerequisites to ensure that the upgrade can be successfully applied. To run precheck, click Run precheck and provide confirmation in the Confirm precheck dialog.
   • Upgrade: Applies the selected upgrade. Oracle recommends that you run the precheck operation for an upgrade before applying it. To apply the upgrade, click Upgrade and provide confirmation in the Confirm dialog.

In the list, the State displays the status of the operation. While an upgrade is being applied, the State displays as Upgrading. The status of the DB system also displays as Upgrading. Lifecycle operations on the DB system and its resources might be temporarily unavailable. If the upgrade completes successfully, the State changes to Applied and the status of the DB system changes to Available.

Perform the following steps to upgrade the Grid Infrastructure of a DB system.

1. Open the navigation menu. Select Oracle Database, then select Oracle Base Database Service.
2. Select your Compartment. A list of DB systems is displayed.
3. In the list of DB systems, click the name of the DB system you want to upgrade. Details of the DB system you selected are displayed.
4. In the DB system information tab, under Version, click the View link beside the Update available field.
5. Under DB system, under Grid Infrastructure updates, review the list of available Grid Infrastructure upgrades for the DB system.

   • The Oracle Grid Infrastructure Software Images tab displays generally available Oracle Grid Infrastructure software images that you can use to upgrade your DB system.

   • The Custom Grid Infrastructure Software Images tab allows you to select a Grid Infrastructure software image you have created in advance.
     • Use the Select a compartment selector to specify the compartment that contains the software image.
     • Use the Region filter to access the software images created in a different region.
6. Click the Actions menu for the upgrade you are interested in, and then click one of the following actions:
   • Run Precheck: Check for any prerequisites to ensure that the upgrade can be successfully applied. To run precheck, click Run precheck and provide confirmation in the Confirm precheck dialog.
   • Upgrade: Applies the selected upgrade. Oracle recommends that you run the precheck operation for an upgrade before applying it. To apply the upgrade, click Upgrade and provide confirmation in the Confirm dialog.

In the list, the State displays the status of the operation. While an update is being applied, the State displays as Updating. The status of the DB system also displays as Updating. Lifecycle operations on the DB system and its resources might be temporarily unavailable. If the update completes successfully, the State changes to Applied and the status of the DB system changes to Available.

Perform the following steps to view the upgrade history of a DB system.

1. Open the navigation menu. Select Oracle Database, then select Oracle Base Database Service.
2. Select your Compartment. A list of DB systems is displayed.
3. In the list of DB systems, click the name of the DB system you want to view the upgrade details. Details of the DB system you selected are displayed.
4. In the DB system information tab, under Version, click the View link beside the Upgrades available field.
5. On the Updates page, click Update history on the left-hand side menu.
6. The history of update and upgrade operations for that DB system is displayed.

Perform the following steps to roll back an unsuccessful upgrade of a DB system.

1. Open the navigation menu. Select Oracle Database, then select Oracle Base Database Service.
2. Select your Compartment. A list of DB systems is displayed.
3. In the list of DB systems, click the name of the DB system you want to view the upgrade details. Details of the DB system you selected are displayed.
4. In the DB system information tab, under Version, click the View link beside the Upgrades available field.
5. On the Updates page, click Update history on the left-hand side menu.
6. The history of update and upgrade operations for that DB system is displayed.
7. When there is an unsuccessful upgrade, an alert message will be displayed at the top of the page.
8. Click Rollback and provide confirmation in the Confirm dialog.