[Definitive Guide] Oracle AI Database 26ai Free (Windows) Installation Instructions

“Oracle AI Database 26ai Free” has finally arrived! As the successor to the traditional “XE (Express Edition)” and “23ai”, this free version is a very powerful tool that allows you to try out the latest AI features (such as Vector Search) right at your fingertips.

However, the Windows version installation has several “pitfalls that you will definitely fall into if you don’t know them.”

Based on the official documentation, this article thoroughly explains the installation procedure to avoid failure, the environment variable settings after installation, and the service settings to keep your PC from slowing down.

⚠️ Important Checklist Before Starting (This is the most important part!)
📂 Installation Procedure: Do Not Create Folders Manually!
⚙️ Post-Installation Environment Variable Settings
🛑 How to Set Service Auto-Start to “Manual” (To Prevent PC Slowdown)
🔌 [Essential Technique] Basic Operations for CDB and PDB (Startup/Shutdown)
❓ Frequently Asked Questions (FAQ)
Summary

⚠️ Important Checklist Before Starting (This is the most important part!)

Before launching the installer, be sure to check the following conditions. If you do not observe these, an error will occur halfway through.

Do you have an old Oracle version installed? If you already have Oracle Database XE or Free, or a database using SID=XE or SID=FREE, be sure to uninstall it. They cannot coexist.

Is it Windows Home Edition? Unfortunately, Home Edition is not supported.

[Most Important] Have you deleted the environment variables? If ORACLE_HOME or TNS_ADMIN remains in the system environment variables, the installation will fail. Be sure to delete them while performing the installation work.

📂 Installation Procedure: Do Not Create Folders Manually!

This is the key point this time.

1. Download and Run the Installer

First, let’s get the installer. You can download it from the official page below.

Download Page: Oracle Database Free Get Started
Target Version: Oracle AI Database 26ai Free
Example Filename: WINDOWS.X64_239000_free.zip

Download Link (Login with an Oracle account may be required for download)

Unzip the downloaded ZIP file and run setup.exe inside as “Run as administrator”.

2. Specify Installation Destination

Specify the installation destination. If default, the following is specified. accel is the OS username. C:\app\accel\product\26ai

✅ Recommended: Proceed with the default, or enter a “folder name that does not exist yet”.
❌ Not Recommended: Specifying a folder you created yourself in Explorer.

Why? Due to Windows security specifications, the Oracle installation folder must not have modification permissions by the Authenticated Users group (all authenticated users). If you create the folder yourself, standard permissions are applied, and the installer will issue an error (or warning). If you let the installer create the folder, it will automatically apply the correct permission settings.

3. Set Password

Set a common administration password for SYS, SYSTEM, and PDBADMIN. Be sure not to forget it.

4. Execute Installation

Finally, check the summary and start the installation. Just in case, make a note of the connection string displayed on the completion screen.

⚙️ Post-Installation Environment Variable Settings

Once the installation is finished, set the environment variables so you can use it comfortably from the command line (SQL*Plus, etc.). Change the paths appropriately according to your environment.

Setting Example (Run in Command Prompt, or set via Environment Variables screen)

:: Database Identifier (Must be FREE for the Free version)
set ORACLE_SID=FREE

:: Oracle Base (Root of installation destination)
:: * The "accel" part is the Windows username. Please change it to match your own username.
:: * "26ai" in the path may differ depending on the version. Check the actual folder.
set ORACLE_BASE=C:\app\accel\product\26ai

:: Oracle Home (Main folder containing executables etc.)
set ORACLE_HOME=C:\app\accel\product\26ai\dbhomeFree

:: Add to Path (Add bin and OPatch)
set PATH=%ORACLE_HOME%\bin;%ORACLE_HOME%\OPatch;%PATH%

I recommend saving this as a .bat file and running it, or setting it permanently from the “Edit the system environment variables” screen in Windows.

🛑 How to Set Service Auto-Start to “Manual” (To Prevent PC Slowdown)

When you install Oracle Database, the default setting is for the database to automatically start up every time you boot your PC. This is fine for servers that run constantly, but for personal learning PCs where you “only want to start it when you want to use it,” I recommend changing the Windows service setting to “Manual”.

1. Open the Services Screen

Search for “Services” in the Windows Start menu, or press Win + R keys, type services.msc, and run it.

2. Find the Target Services

Look for the following services in the list (it is easier to find if you sort by name).

OracleServiceFREE (Important! This is the database body)
OracleOraDB26Home1TNSListener (Listener The number part of the name may differ depending on the version)
OracleVssWriterFREE (For VSS Backup)
- This is usually for integrating with Windows backup features. For personal learning purposes, there is no problem stopping it (setting to manual).

3. Change to “Manual”

Right-click the target service (especially OracleServiceFREE which consumes memory) and open “Properties”. Change “Startup type” to “Manual”. Click “OK” to close.

4. Correct Order for Manual Start/Stop (Important)

There is a correct order for starting and stopping the service and the database body (instance). Failure to observe this may cause data corruption or connection errors.

✅ Order when Starting

Start Service → 2. Database becomes usable

:: 1. Start the listener first
net start OracleOraDB26Home1TNSListener

:: 2. Next, start the database service
net start OracleServiceFREE

After starting the service, the database will become available after a short while.

🛑 Order when Stopping

Stop Database (SQL) → 2. Stop Service

If you force stop the service (net stop) suddenly, there is a risk of disconnection during data writing. Be sure to stop it safely with SQL*Plus, then take down the service.

Stop with SQL*Plus (See “Basic Operations” below for details) shutdown immediate
Stop the service net stop OracleServiceFREE net stop OracleOraDB26Home1TNSListener

🔌 [Essential Technique] Basic Operations for CDB and PDB (Startup/Shutdown)

Oracle Database Free has a two-tier structure: CDB (Parent Database) and PDB (Child Database). When you start the Windows service (net start), the parent (CDB) starts, but the child (PDB) may not open automatically.

Here, I will introduce the minimum operation methods using SQL*Plus.

1. Connection and Startup of the Database

First, ensure that the Windows service (OracleServiceFREE, etc.) is running. Connect to the entire database (CDB) with administrator privileges.

sqlplus / as sysdba

If the service is running but the DB is stopped (connected to an idle instance), start it with the following command.

startup

2. Checking and Opening PDB (Pluggable Database)

Check the status of the PDBs.

show pdbs

If MOUNTED is displayed, it is in a state where it cannot be used yet (closed state). Execute the following command to open all PDBs (READ WRITE).

alter pluggable database all open;

(Below is the execution log)

C:\Users\accel>set %ORACLE_SID%=FREE

C:\Users\accel>set %ORACLE_BASE%=C:\app\accel\product\23ai

C:\Users\accel>set %ORACLE_HOME%=C:\app\accel\product\23ai\dbhomeFree

C:\Users\accel>set %PATH%=%ORACLE_HOME%\bin;%ORACLE_HOME%\OPatch;%PATH%

C:\Users\accel>sqlplus / as sysdba

SQL*Plus: Release 23.0.0.0.0 - Production on 月 12月 29 14:53:52 2025
Version 23.9.0.25.07

Copyright (c) 1982, 2025, Oracle.  All rights reserved.

Connected to an idle instance.

SQL> startup
The ORACLE instance has started.

Total System Global Area 1603491808 bytes
Fixed Size                  5126112 bytes
Variable Size             419430400 bytes
Database Buffers         1174405120 bytes
Redo Buffers                4530176 bytes
The database is mounted.
The database has been opened.
SQL> show pdbs

    CON_ID CON_NAME                       OPEN MODE  RESTRICTED
---------- ------------------------------ ---------- ----------
         2 PDB$SEED                       READ ONLY  NO
         3 FREEPDB1                       READ WRITE NO
SQL> alter pluggable database all open;

A pluggable database has been altered.

SQL> show pdbs

    CON_ID CON_NAME                       OPEN MODE  RESTRICTED
---------- ------------------------------ ---------- ----------
         2 PDB$SEED                       READ ONLY  NO
         3 FREEPDB1                       READ WRITE NO  ★

3. [Super Convenient] Setting PDB to Open Automatically Next Time

It is troublesome to type alter pluggable database... every time, isn’t it? If you execute the following command with the PDBs open, the PDBs will automatically open the next time the CDB starts.

alter pluggable database all save state;

4. Stopping the Database

To safely stop the database before shutting down your PC, etc., execute the following command. After stopping, it is recommended to stop the Windows service as well to free up PC resources (procedure described above).

shutdown immediate
exit

shutdown abort is a forced termination, so please avoid it except in emergencies.

❓ Frequently Asked Questions (FAQ)

From here, I will answer questions often asked by readers (presumably) in advance from a professional perspective!

Q1. I want to set the installation destination to C:\dbfree, so I created the folder in advance. Is that okay? A. I do not recommend it (or rather, stop doing it). If you create it manually, change permissions for “Authenticated Users” will be attached. To remove this, complex permission operations with the icacls command are required. The easiest way is to delete the folder, enter C:\dbfree on the installer screen, and let the installer create and configure it.

Q2. Can I change ORACLE_SID to XE like the previous XE? A. No, you cannot. In Oracle AI Database Free, the SID is fixed to FREE. Other SIDs are not allowed. Please specify localhost:1521/FREE etc. when connecting.

Q3. I got an error when installing as a domain user. A. Are you connected to the network? In the case of a domain user, you need to be able to communicate with the domain controller during installation (VPN, etc.). If you cannot connect to the network, create a local administrator user and log in with that user to install.

Q4. It fails at “Prerequisite Checks” during installation. A. Does the environment variable ORACLE_HOME remain? This is the most common cause. Old settings left behind will interfere. Delete them cleanly from the settings screen, and then run setup.exe again.

Summary

Installation of Oracle AI Database 26ai Free is comfortable if you observe the following three points!

Clean up environment variables (Before installation)
Let the installer create folders (Avoid permission troubles)
Change services to manual startup (PC optimization)

Let’s finish the environment setup quickly and enjoy the latest AI features and the world of SQL!