by Brian Fitzgerald

Introduction

Your Red Hat kernel got upgraded and now AFD does not load. Solution: run “grubby –set-default”. This article applies to Oracle Database 19c on Red Hat Enterprise Linux 9 on-premises.

Background

ASM filter driver (AFD) requires loading kernel module oracleafd.ko. The kernel modules are distributed in release updates and are installed in $ORACLE_HOME/usm/install/Oracle. AFD kernel modules are tied to a specific sub-version of Red Hat EL 9, and Oracle’s distribution of new AFD kernel modules may lag the Red Hat release by 6 months. For example, rhel9_4 was released on April 30, 2024, but Oracle did not release the compatible AFD kernel module until RU 19.25 of October 15, 2024. If you issued “dnf update” or “yum update” after April 30, but before installing RU 19.25, then AFD has stopped working. You must downgrade your kernel. Refer to ACFS and AFD Support On OS Platforms (Certification Matrix). (Doc ID 1369107.1) for up-to-date AFD kernel driver release information.

rhel9_5 was released on November 13, 2024. If you issued “dnf update,” then AFD has stopped working. As of this writing, Oracle has not released an rhel9_5 AFD kernel module, so you must downgrade your kernel.

Don’t do it!

Don’t run “dnf update”!

Oh no, you did it!

“dnf update” got run and now AFD does not load. Your Oracle database is down!

Fix it!

Fix this issue simply by identifying your previous kernel file and running “grubby –set-default”. Reboot.

Yay, it’s fixed!

Notice that filtering is not supported on Red Hat 9. Be careful not to overwrite your ASM device!

No filtering in RHEL9

ASM filter driver is designed to block IO from programs except for Oracle binaries. Filtering works in rhel7. You can’t overwrite an oracle device with dd, for example:

Refer to Oracle Automatic Storage Management Filter Driver (ASMFD) (Doc ID 2806979.1) for news about AFD filtering. Exercise care when handling Oracle devices. For example:

dd overwrote /dev/nvme3n1. Your data is wiped out. The ironically named “ASM Filter Driver” did not filter the non-Oracle I/O.

Common SA commands such as parted could corrupt your disk:

Be careful!

Red Hat release

Notice that the kernel is at rhel9_4, but the operating system is at rhel9_5.

Conclusion

We covered these points:

• Oracle AFD depends on a kernel module.
• In Red Hat 9, the AFD kernel module is tied to a specific sub-version.
• Oracle will release the needed AFD module after each Red Hat 9 sub-version release.
• Depending on what Oracle RU you have installed, dnf update may install a kernel that is incompatible with your AFD module.
• You can fix your problem by running “grubby –set-default”
• You can upgrade to a specific kernel version.
• ASM filter driver no longer filters.
• Administrative commands could wipe out your disks.
• Exercise greater care without filtering present.