15 Mar Will Oracle Database links really stop working after April 2019 (or June 2019)?

Posted at 14:56h in Oracle by

UPDATED November 2018

On February 15th 2018 Oracle published note 2361478.1 (“Oracle Databases Need to be Patched to a Minimum Patchset/PSU/RU level before April 2019”), stating that database versions prior to 12.1.0.2 (except for 11.2.0.4) will need additional patching in order to be able to use database links after April 2019.

This caused some confusion for Oracle database users who thought that database links would not work anymore after April 2019 if no additional patch was installed. Moreover, what about Oracle 10g R2 and older, those editions are not supported anymore so no additional patches will be released?

In October 2018 there was an update: April 2019 has been replaced by June 2019 (“Recommended patches and actions for Oracle databases versions 12.1.0.1, 11.2.0.3 and earlier – before June 2019”), to be more precise, affected databases should be patched before June 23rd 2019. On this date, changes in the maximum SCN limit will happen.

Oracle also released a note with additional information: 2335265.1 (“Recommended patching and actions for Oracle database versions 12.1.0.1, 11.2.0.3 and earlier – before June 2019”). This note tells us the following:

  • Versions 11.2.0.4, 12.1.0.2 or higher and 12.2.0.1 or higher already include the fixes needed
  • All 11g R2 (11.2) versions need to be upgraded/patched to at least version 11.2.0.3.9. It’s even better to upgrade to 11.2.0.4 or higher (preferably 12c R2)
  • All 11g R1 (11.1) versions need to be upgraded/patched to at least version 11.1.0.7.20. It’s even better to upgrade to 11.2.0.4 or higher (preferably 12c R2)
  • Database Links between unpatched databases or between older releases are not affected by this change. However, it’s still recommended to upgrade to a higher version (for security purposes, for support, etc…).
  • Database Links between an unpatched/old release database and a patched/newer version might encounter errors (for some cases) at any point in time, after June 23rd

So this already makes it easier to determine the impact on your Oracle Database environment. For versions prior to 12.1 one should check the DB links via the DBA_DB_LINKS view and make the linking to check if patching will be needed or not.

Starting from version 12.1, one can find any incoming database links via a query on the DBA_DB_LINK_SOURCES view, which can save some time finding the existing database links between databases.

Why will this only happen after June 2019?

The patches which need to be installed, make it possible to support increased maximum SCN limit. However, the increased maximum SCN limit only becomes effective after June 23rd 2019. That’s why.

The maximum SCN limit is calculated at any point in time based on the number of seconds elapsed since 1988. This way of working allows over 500 years of data processing for any Oracle Database. Versions 11.2.0.4 and 12.1.0.2 or higher enable the databases to allow a higher current maximum SCN limit and so support a transaction rate which is many times higher than earlier releases.

When using an older unpatched version which uses database links to patched versions (including versions 11.2.0.4 and/or 12.1.0.2 or higher) after June 23rd 2019, the link could possibly encounter issues or even cannot be established, because versions including the increased maximum SCN limit could be running on a much higher SCN level not supported by the older and unpatched versions.

So patching is not required for database links to work after June 2019, but will you take the risk when having database links between unpatched and patched versions?

Do you still have questions about this patching? Not sure this patching is really needed? In need for some help in getting the entire picture of Oracle database links used within your organization? Just ask us for more information or help about the Oracle database links and potential patching for your Oracle database environment.