Upgrading Oracle Grid Infrastructure (GI) from 19c to 26ai (23c internally) is a critical task for RAC environments. While Oracle provides documentation, real-world execution often requires additional clarity.

In this guide, I will walk through a complete step-by-step upgrade of a 2-node RAC cluster, using actual commands and logs from a real upgrade scenario.

• Nodes: ram1, ram2
• Source Version: Oracle 19c GI
• Target Version: Oracle 26ai (23.x)
• Grid Home:
• Old: /u01/app/19c/grid
• New: /u01/app/grid26
• OS: Linux (systemd-based)

Step 1: Download and Extract 26ai Grid Home

mkdir -p /u01/app/grid26
chown -R grid:oinstall /u01/app/grid26
unzip LINUX.X64_26ai_grid_home.zip -d /u01/app/grid26

Step 2: Setup New Grid Home (Software Only)

./gridSetup.sh -silent -setupHome \
-OSDBA oinstall \
-OSASM asmadmin \
-ORACLE_BASE /u01/app/gi_base

Step 3: Run Prechecks

/u01/app/grid26/bin/cluvfyrac.sh stage -pre crsinst -n ram1,ram2 -verbose

Step 4: Resolve Mandatory Prerequisites

From logs:

[FATAL] [INS-13019]
- Disk group RDBMS compatibility setting
- Grid Infrastructure Management Repository cleanup

Fix Diskgroup Compatibility

ALTER DISKGROUP DATA SET ATTRIBUTE ‘compatible.rdbms’=’19.0.0.0.0’;

Remove GIMR (MGMTDB)

srvctl stop mgmtdb -f
srvctl remove mgmtdb -f

Step 5: Start Upgrade

/u01/app/grid26/gridSetup.sh -silent -ignorePrereqFailure -upgrade

Step 6: Run Root Upgrade (Node1 First)

/u01/app/grid26/rootupgrade.sh

Step 7: Fix init Script Issue (Important for OL8/OL9)

Error encountered:

restorecon: /etc/init.d/init.ohasd not found

Fix

touch /etc/init.d/init.ohasd
touch /etc/init.d/ohasd
chmod 755 /etc/init.d/*
restorecon -Rv /etc/init.d

Step 8: Rerun Root Script

/u01/app/grid26/rootupgrade.sh

Step 9: Upgrade Node2 (Last Node)

/u01/app/grid26/rootupgrade.sh

Step 10: Handle Non-Blocking Messages

Example:

CRS-1115: Oracle Clusterware has already been upgraded

Step 11: Final Verification

Check Cluster Version

crsctl query crs activeversion

Expected:

23.0.0.0.0

This step-by-step guide demonstrates how to successfully upgrade Oracle RAC Grid Infrastructure from 19c to 26ai using real-world commands and logs.

With proper preparation and troubleshooting, the upgrade can be completed smoothly with minimal disruption.