You made it! You’ve upgraded your database.

But before allowing users back in, let’s do a few final touches.

Backup

Start a backup of your database:

• Preferably a level 0 backup, otherwise, a level 1 backup.
• It doesn’t have to finish inside your maintenance window.
• Although it is possible to restore a backup from the previous release and recover across an upgrade, it complicates the process.

If you also converted your database to a PDB:

• You just need a backup of the new data files, not the entire CDB.
• Backups taken while the database was a non-CDB (i.e., before the plug-in) are called preplugin backups. Although it is possible to restore and recover using a combination of preplugin backups and CDB backups, it complicates the process a lot.
• You should practice using preplugin backups.
• AutoUpgrade automatically runs the DBMS_PDB.EXPORTRMANBACKUP during a non-CDB to PDB conversion. This ensures that the backup metadata is transferred into the new PDB. This eases the use of preplugin backups.

Gather Fixed Objects Statistics

Fixed objects statistics are on those weird X$ structures in the database. You must refresh them after upgrade.

• Fixed objects vary in size and shape based on your workload.
• You must never gather fixed objects statistics right after a database restart. Only after a while, when the database is warmed up with a representative workload.
• As an example, there are structures related to the buffer cache. After a restart, the buffer cache is empty. After your workload, the buffer cache is full. You want those stats to reflect the full buffer cache.

So, come back to your database after a while and re-gather the stats. Since you’ll probably forget that, here’s how to do it via a scheduler job. AutoUpgrade can even create that job for you.

Parameters

I want to highlight an underscore parameter.

But you don’t want to set underscore parameters in your database, because some random dude on the internet says so. So, please check the corresponding MOS notes.

_cursor_obsolete_threshold

In Oracle Database 12.2, this parameter was raised from 1024 to 8192 to support CDBs with thousands of PDBs. But you don’t have that.

I’ve seen this change cause severe issues in non-CDBs and even CDBs with many PDBs.

Unless you have hundreds of PDBs in your CDB, set the following value:

alter system set "_cursor_obsolete_threshold"=1024 scope=spfile;

Ref.: High Version Counts For SQL Statements (>1024) Post Upgrade To 12.2 and Above Causing Database Slow Performance (Doc ID 2431353.1)

Optimizer Fixes – Installed But Disabled

Many of the optimizer fixes in your database are turned off. Yeah, that’s right. Oracle delivered a fix for an optimizer problem, but turned the fix off.

Optimizer fixes that have the potential to change an execution plan are not enabled. This ensures plan stability when you patch. The idea is that you only enable the fixes for problems you see in your database. Otherwise, you live without the fix and don’t have to worry about changing plans.

But when you upgrade to a new release, you want to benefit from all those optimizer fixes. After all, Oracle added the fixes for a reason. When you upgrade, you test your application, and you have time to fix any issues.

In Oracle AI Database 23.26.0, there are 108 optimizer fixes that are turned off. You can find a list in ORAdiff (under Included Fixes and Fix Control).

1. Perform a test upgrade.
2. Enable all optimizer fixes.

   execute dbms_optim_bundle.enable_optim_fixes('ON','BOTH', 'YES');
   

3. Test your application.
4. Upgrade the production database.
5. Enable the same optimizer fixes as in #2.

Data Guard

Check your Data Guard configuration:

• Ensure standbys have caught up and are ready to take over.
• Use the Data Guard broker command VALIDATE DATABASE to check each database in your configuration.

If you also converted your database to a PDB:

• The plug-in operation has a different effect on standbys depending on whether you plug in with enabled or deferred recovery. It’s imperative that you check your Data Guard configuration.
• Use the Data Guard broker command VALIDATE DATABASE to check each database in your configuration.
• I recommend doing a switchover to each of your standbys and opening the PDB on each of the databases. The VALIDATE DATABASE command will not reveal all the pitfalls.
• My team discussed this in our webinar Move to Oracle Database 23ai – Everything you need to know about Oracle Multitenant – Part 1.

What Else

I’m sure your runbook has lots of other steps. Remember, you can automate many of them using an after action script in AutoUpgrade.

Check the other blog posts related to upgrade to Oracle AI Database 26ai.

Happy upgrading!

Before the upgrade fun can begin, we need a new Oracle home. But that’s so easy using AutoUpgrade.

Download Software and Patches

In Oracle AI Database 26ai, Oracle delivers updated gold images, so there’s no need to manually download the base release.

• I create a new AutoUpgrade config file:

  global.global_log_dir=/home/oracle/autoupgrade/log
  global.keystore=/home/oracle/autoupgrade/keystore
  global.folder=/home/oracle/patch-repo
  download1.target_version=23
  download1.patch=RECOMMENDED,JDK,37393792
  download1.platform=LINUX.X64
  

  • The patch parameter instructs AutoUpgrade to download
    • RECOMMENDED gives me the newest gold image, including an updated OPatch and OCW component. Further, it brings in the matching Data Pump bundle patch. The OJVM component is now fully embedded in the Release Update.
    • JDK adds a one-off patch that updates the JDK installation in the Oracle home to the very latest version.
    • I can add additional one-off patches by specifying the patch number.
    • In a later version of AutoUpgrade, you can set target_version to 26 as well. But until then, use 23.
• I’ve already stored my MOS credentials in the AutoUpgrade keystore.
• Now, I can download the patches:

  java -jar autoupgrade.jar -patch -config download-software.cfg -mode download
  

Install Oracle Home

Now that we have the software and patches, let’s install an Oracle home. You can use AutoUpgrade for that as well – even for Oracle RAC databases.

• I create a new config file:

  global.global_log_dir=/home/oracle/autoupgrade/log
  global.keystore=/home/oracle/autoupgrade/keystore
  global.folder=/home/oracle/patch-repo
  install1.target_version=23
  install1.patch=RECOMMENDED,JDK,37393792
  install1.target_home=/u01/app/oracle/product/dbhome_26
  install1.home_settings.oracle_base=/u01/app/oracle
  install1.home_settings.edition=EE
  install1.home_settings.inventory_location=/u01/app/oraInventory
  install1.download=no
  

  • I specify the location of my Oracle home using target_home.
  • The above-mentioned home_settings are mandatory. I can customize the Oracle home using additional parameters. Check the documentation for further details.
• Now, I can install the new Oracle home:

  java -jar autoupgrade.jar -patch -config install-oh.cfg -mode create_home
  

• If my oracle user has sudo privileges, AutoUpgrade runs the root scripts for me. Otherwise, it will print a message in the console.

  # Run the root.sh script as root for the following jobs:
  For create_home_1 -> /u01/app/oracle/product/dbhome_26/root.sh
  

• I now have a fully up-to-date Oracle home:

  $ OPatch/opatch lspatches
  37393792;ORA-12850 REPORTED AFTER APPLYING DBRU ON FIRST NODE
  38378853;JDK BUNDLE PATCH 23.26.0.0.0
  38504058;DATAPUMP BUNDLE PATCH 23.26.0.0.0
  38405123;OCW RELEASE UPDATE 23.26.0.0.0 (38405123) Gold Image
  38404116;Database Release Update : 23.26.0.0.0 (38404116) Gold Image
  
  OPatch succeeded.
  

• Consider creating a gold image to use on another server. In a future release, AutoUpgrade will be able to do that too.

Happy upgrading!

Further Reading

• Upgrade to Oracle AI Database 26ai
• AutoUpgrade New Features: Install Oracle Home on Brand-New, Empty Server

Here is a list of things to check and carry out while preparing for Oracle AI Database 26ai.

These tasks are not mandatory, but I recommend them based on my experience. It increases your chances of upgrading successfully.

Weeks Before

Versioning

Oracle AI Database 26ai introduces a new versioning schema. Although 26ai replaces 23ai, in the database, the version remains the same:

After upgrade to 26ai, the version remains 23.0.0.0.0:

SQL> select version from v$instance;

VERSION
-------
23.0.0.0.0

If you check version_full, you’ll see that the second digit reflects the new version:

SQL> select version_full from v$instance;

VERSION
-------
23.26.0.0.0

Platform Certification

Ensure that the new release supports your operating system. When available, you can check it in the installation guides. However, you can find the most up-to-date information in the Product Certification Matrix tab in My Oracle Support.

Clients

Check which clients are connecting to the database and ensure their client driver versions are compatible with Oracle AI Database 26ai. The client/server interoperability matrix gives you an overview of which clients work with which servers.

Client	Database 26ai	Database 19c
26ai	Yes	Yes
21c	Yes	Yes
19c	Yes	Yes
18c	No	Yes
12.2.0.1	No	Yes
12.1.0.2	No	Yes
11.2.0.4	No	Yes

19c supports much older clients compared to 26ai. If you’re using such old clients, start upgrading them right away. This also applies to database links.

Optionally, monitor the database over time to generate a list of clients connecting.

AutoUpgrade

Get the latest version of AutoUpgrade from My Oracle Support. I recommend that you always use the latest version. AutoUpgrade is fully backward compatible, so any newer version can upgrade older releases of Oracle AI Database.

Upgrade Readiness

Run AutoUpgrade in analyze mode to determine your database’s upgrade readiness. Check the summary report for findings with no fixups. Such findings must be dealt with manually.

You can run the analysis even before you install the new Oracle home. Simply specify target_version=26 in your AutoUpgrade config file, and AutoUpgrade knows which checks to run.

Dictionary Check

Check the dictionary in your most important databases. You can run a dictionary check together with an AutoUpgrade analysis. In your config file:

upg1.run_dictionary_health=full

Or, you can run it separately using DBMS_DICTIONARY_CHECK.

Behavior Changes

Review the upgrade guide for information on deprecated and desupported features, plus any behavior changes.

Also, use ORAdiff to check for changes between your current release and 26ai. Use the Report menu item to generate a report that you can share with your company.

It’s also a good idea to look at the new reserved keywords. Especially, those marked as reserved. Don’t use those keywords in object/column names, queries, or the like.

Grid Infrastructure

• If Grid Infrastructure manages your database either in RAC or Oracle Restart configuration, you should upgrade it as well. If you can tolerate an additional maintenance window, I’d recommend upgrading Grid Infrastructure in advance.

• Grid Infrastructure 26ai can manage databases from 19c and onwards. Any older database must be moved away from the system.

• I recommend keeping the GI and database patch levels in sync. If you want to upgrade the database to 26.1, then upgrade GI to the same Release Update. If that’s not possible, at least keep it within two Release Updates.

Days Before

Statistics

Gather dictionary and fixed objects statistics:

begin
   dbms_stats.gather_fixed_objects_stats;
   dbms_stats.gather_schema_stats('SYS');
   dbms_stats.gather_schema_stats('SYSTEM')
end;

• I prefer gathering schema stats rather than dictionary stats. I’ve seen a few edge cases solved by schema stats, and generally, current stats on SYS and SYSTEM are sufficient.

• Gather statistics no earlier than seven days before the upgrade. If AutoUpgrade determines your statistics are older than that, it will gather them as part of the upgrade. This extends downtime unnecessarily.

• If you’re curious, you can find details about the importance of fixed objects statistics in a blog post by Maria Colgan.

Install Oracle Home

You can use AutoUpgrade to:

• Download the software and patches.
• Install the Oracle home.

In release 26ai, the Oracle homes that you download are already patched with the latest Release Update and OPatch.

On the Day of Upgrade

Backup

If time allows, run a level 0 backup. If not, you have to settle with a level 1.

Don’t run the backups inside your maintenance windows; that’s a waste of downtime. Start the backup in advance, so it finishes just before the maintenance window begins.

AutoUpgrade automatically creates a guaranteed restore point before starting the upgrade.

Scheduler

Normally, it is not necessary to disable the scheduler. But in some situations, it can be beneficial.

That’s It

You are now ready to begin your journey to Oracle AI Database 26ai and its many exciting new features.

Check the other blog posts related to upgrade to Oracle AI Database 26ai.

Happy upgrading!

Get ready for the future and enjoy the many new cool features in Oracle AI Database 26ai. It is just an upgrade away.

This blog post gives you a quick overview of the upgrade to Oracle AI Database 26ai. Plus, it is the starting point of a whole series of blog posts with all the details.

Things to Know

• You can upgrade to Oracle AI Database 26ai if your database runs 19c or 21c.

  • If you have an older database, you must first upgrade to 19c and then upgrade again to 26ai.
  • If you’re on 23ai, you can just patch the database; no upgrade needed, no need to re-certify your app.

• Oracle AI Database 26ai supports the multitenant architecture only. If your database is a non-CDB, you must also convert it to a pluggable database as part of the upgrade.

• Although the Multitenant Option requires a separate license, you can still run databases on the multitenant architecture without it. Oracle allows a certain number of pluggable databases in a container database without the Multitenant Option. Check the license guide for details, and be sure to set max_pdbs=3 if you don’t have the license.

• Oracle AI Database 26ai is the next long-term support release. It means you can stay current with patches for many years. At the time of writing, Premier Support ends in December 2031, but check Release Schedule of Current Database Releases (Doc ID 742060.1) for up-to-date information.

• In Oracle AI Database 26ai, AutoUpgrade is the only recommended tool for upgrading your database. Oracle desupported the Database Upgrade Assistant (DBUA).

• You can also use Data Pump or Transportable Tablespaces to migrate your data directly into a 26ai PDB. Even if the source database runs on a lower release and in a non-CDB. In fact, you can export from Oracle v5 and import directly into a 26ai PDB.

Important Things about Multitenant Migration

• The multitenant conversion is irreversible. Not even Flashback Database can help if you want to roll back. You must consider this when planning for a potential rollback.
• For smaller databases, you can rely on RMAN backups. However, for larger databases, a restore may take too long.
• For rollback, you can use a copy of the data files:
  • The CREATE PLUGGABLE DATABASE statement has a COPY clause, which copies the data files and uses the copies for the new PDB.
  • Refreshable clone PDB can minimize the time needed to copy the data files by doing it in advance and rolling forward with redo.
  • Use image copies of your data files and roll forward with RMAN.
  • Use a standby database for rollback.
  • Storage snapshots
• Depending on your Data Guard configuration, the plug-in operation needs special attention on your standby databases. If you have standby databases, be very thorough and test the procedure properly.
• In the worst case, you can break your standby databases without knowing it. Be sure to check your standby databases at the end of the migration. I recommend performing a switchover to be sure.
• The multitenant conversion requires additional downtime. Normally, I’d say around 10-20 minutes of additional downtime. But if you have Data Guard and must fix your standby databases within the maintenance window, then you need even more time.

And Then …

Over the coming months, I will publish several blog posts with step-by-step instructions and other info. Stay tuned!

By the way, this blog post was originally posted a while ago for Oracle Database 23ai, but we all know what happened there. So, let’s start over with Oracle AI Database 26ai.

Happy upgrading!

Other Blog Posts

• How to Prepare Your Oracle Database for Release 26ai
• Install a New Oracle home for Oracle AI Database 26ai
• How I Think You Should Create Your Container Databases
• Important Things after Upgrading to Oracle AI Database 26ai

Non-CDB

• Upgrade Oracle Database 19c Non-CDB to 26ai and Convert to PDB

• Upgrade Oracle Database 19c Non-CDB to 26ai and Convert to PDB Using Refreshable Clone PDB

• Upgrade Oracle Database 19c Non-CDB to 26ai and Convert to PDB with Data Guard and Re-using Data Files (Enabled Recovery)

• Upgrade Oracle Database 19c Non-CDB to 26ai and Convert to PDB with Data Guard and Restoring Data Files (Deferred Recovery)

CDB

• Upgrade Oracle Database 19c CDB to 26ai

• Upgrade Oracle Database 19c CDB to 26ai with Data Guard

PDB

• Upgrade Oracle Database 19c PDB to 26ai

• Upgrade Oracle Database 19c PDB to 26ai using Refreshable Clone PDB

• Upgrade Oracle Database 19c PDB to 26ai with Data Guard using Refreshable Clone PDB

• Upgrade Oracle Database 19c PDB to 26ai with Data Guard and Re-using Data Files (Enabled Recovery)

• Upgrade Oracle Database 19c PDB to 26ai with Data Guard and Restoring Data Files (Deferred Recovery)

OCI

• Upgrade Oracle Base Database Service to Oracle AI Database 26ai
• Upgrade Pluggable Database to Oracle AI Database 26ai
• Upgrade Exadata Database Service and Exadata Cloud@Customer (external blog, Alex Zaballa)