How to Resolve OPatch “CheckActiveFilesAndExecutables” Error on Oracle Client for Windows

When applying an Oracle Client patch on Windows, you may encounter the following OPatch error:

Prerequisite check "CheckActiveFilesAndExecutables" failed.
Following active files/executables/libs are used by ORACLE_HOME

This error occurs because one or more applications are currently using DLLs from the Oracle Client Home, preventing OPatch from updating them.

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Environment

• Oracle Client: 19c
• Operating System: Windows Server
• OPatch Version: 12.2.0.1.52

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Error Message

While running:

C:\app\client\Administrator\product\19.0.0\client_1\OPatch\opatch apply

OPatch returned:

Prerequisite check "CheckActiveFilesAndExecutables" failed.

It also listed several Oracle DLLs in use, including:

• oci.dll
• oraons.dll
• oracore19.dll
• oracommon19.dll
• orapls19.dll
• oraxml19.dll

This indicates that another process is actively using the Oracle Client installation.

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Step 1 – Identify the Process Using Oracle DLLs

Open PowerShell or Command Prompt as Administrator and execute:

tasklist /M oci.dll

Example output:

Image Name                     PID     Modules
========================= ======== ===================
PRIME Jobs Administrator.   6844     OCI.dll
hsmisserver.exe             5808     OCI.dll
km.exe                      2260     OCI.dll
Online Administration.exe   6172     OCI.dll
PRIME Jobs Administrator.   3328     OCI.dll

The command displays all processes currently loading OCI.dll, confirming which applications are locking the Oracle Client Home.

Tip: You can also search for other Oracle DLLs such as oraons.dll or oracore19.dll if needed.

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Step 2 – Stop or Kill the Processes

After identifying the processes, close the applications gracefully if possible.

If they cannot be closed normally, terminate them using their Process ID (PID):

taskkill /PID 6844 /F
taskkill /PID 5808 /F
taskkill /PID 2260 /F
taskkill /PID 6172 /F
taskkill /PID 3328 /F

Alternatively:

taskkill /IM hsmisserver.exe /F

Important: Ensure these applications are safe to stop and coordinate with the application owners before terminating production services.

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Step 3 – Verify No Oracle DLLs Are Locked

Run the command again:

tasklist /M oci.dll

If no processes are returned (or only expected ones remain), the Oracle Home is no longer in use.

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Step 4 – Apply the Patch Again

Re-run OPatch:

cd C:\Users\administrator.PEOPLESBANK\Desktop\Patch\38818049

C:\app\client\Administrator\product\19.0.0\client_1\OPatch\opatch apply

This time, the patch should proceed successfully.

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Why This Happens

Oracle Client DLLs such as OCI.dll are shared libraries used by many third-party applications. Any application connected to an Oracle database using the Oracle Client will load these DLLs into memory.

Common examples include:

• Custom Windows services
• Banking or enterprise applications
• SQL*Plus
• Toad
• PL/SQL Developer
• SQL Developer (OCI connections)
• Middleware or integration services

As long as these DLLs remain loaded, Windows prevents OPatch from replacing them.

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Useful Commands

Find processes using OCI.dll

tasklist /M oci.dll

Find processes using another Oracle DLL

tasklist /M oraons.dll

Kill a process by PID

taskkill /PID <PID> /F

Kill a process by name

taskkill /IM processname.exe /F

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Conclusion

The CheckActiveFilesAndExecutables prerequisite failure is one of the most common issues encountered when patching Oracle Client on Windows. Instead of rebooting the server, you can quickly identify the applications locking the Oracle Home by using:

tasklist /M oci.dll

After stopping or terminating the identified processes, rerun OPatch and the patch installation should complete successfully. This simple troubleshooting method can save valuable maintenance time and minimize downtime during Oracle Client patching.