Category Archives: 23ai

23ai, new parameters DB_FLASHBACK_LOG_DEST_SIZE and DB_FLASHBACK_LOG_DEST

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Oracle database has the Oracle Flashback Technology that allows you to view old images of your data without the need to restore your database. You can use restore points, restore tables, and rows, and do a lot of things. To use it (in a simple way), you need to enable the archivelog and flashback mode for your database and Oracle will create additional logs while you change the data.

Unfortunately, it is exactly these logs that create some issues. Jonathan Lewis already described this issue, and in resume, while changing the data you need to write more because you will use UNDO + Flashback logs. In essence, you write more every time. 

Until Oracle 23ai, it was not possible to change the place where you write these logs, (more or less) it will always be where you write your archivelogs (when using the fast recovery area). So, archivelogs and flashback logs are tight where they reside. Luckily this changed, and the new features of 23ai explain:

The idea is to put the flashback logs in a dedicated (and fast) disk to reduce the impact of writing them.

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Upgrading to GI 23ai at ExaCC using CLI

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As you know, the 23ai is already available in several environments, mainly in Oracle Cloud, and one of these is the ExaCC. I already covered how to do the upgrade to 23ai for Grid Infrastructure (GI) using the Web interface, and Christian covered the upgrade of the OCI CLI. But here I will upgrade using the ExaCC CLI (dbaascli).

Again, first things first. Requirements

As discussed in the previous post, the first requirement is that your VM/domU is running the 23.1x version because it runs over the OEL 8. The second one is that the only available versions that are allowed to be installed in the cluster are the 19c and 23ai. The last one is that the attribute “compatible.rdbms” needs to be at least 19.0.0.0 for your diskgroups:

SQL> SELECT name, compatibility, database_compatibility FROM v$asm_diskgroup;

NAME                           COMPATIBILITY                                                DATABASE_COMPATIBILITY
------------------------------ ------------------------------------------------------------ ------------------------------------------------------------
DATAC5                         19.0.0.0.0                                                   11.2.0.4.0
RECOC5                         19.0.0.0.0                                                   11.2.0.4.0

SQL>
SQL> ALTER DISKGROUP DATAC5 SET ATTRIBUTE 'compatible.rdbms' = '19.0.0.0.0';

Diskgroup altered.

SQL> ALTER DISKGROUP RECOC5 SET ATTRIBUTE 'compatible.rdbms' = '19.0.0.0.0';

Diskgroup altered.

SQL>

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Upgrading to GI 23ai at ExaCC

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The 23ai was released last month and was only available at Oracle Cloud deployments and a few places for free edition, nothing besides that. Last year it was also released (focused on the Devs) as a formerly 23c free edition. Fortunately, it was released to be used at ExaCC. So, now we can upgrade Grid Infrastructure (GI) and install the database to play with it.

In all previous scenarios, we had some constraints. For Dev’s we didn’t have RAC, DG, and GI features at all. And for OCI, we didn’t have access to manually create databases or deploy GI buy ourselves. For ExaCC we are free to deploy our GI, install RAC databases, and so on. Here I will show how to upgrade your GI from 19c to 23ai. We will reach this:

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