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Fix Access ODBC ORA-12638 Credential Retrieval Failed Error

Maira Mehtab Sep 20, 2026 869 views

Question details

The user needs to resolve an ORA-12638 credential retrieval failed error preventing Microsoft Access from connecting to an Oracle database via ODBC.

Product: Microsoft Access and Oracle Database
Device & OS: not provided
Scenario: Attempting to connect Microsoft Access to an Oracle database in an environment with multiple Oracle clients and both 32-bit and 64-bit ODBC administrators.
Observed behavior: Access fails to establish the connection and displays the ORA-12638 error, even though the database can be successfully reached through ODBC using other tools like LinqPad.

Before you start

Verify whether your Microsoft Access installation is 32-bit or 64-bit to ensure you configure the correct ODBC Data Source Administrator before modifying connection settings.

Solution 1Recommended

Recreate Linked Tables with Matching Architecture

Ensure you are using the correct ODBC administrator architecture that matches your Access version and recreate the database links.

In environments running both 32-bit and 64-bit tools, architecture mismatch is a common cause of ODBC connection failures. Access requires the ODBC driver and Data Source Name (DSN) bit-version to match its own installation exactly.

Identify Access Architecture

Open Microsoft Access, navigate to File > Account > About Access, and check whether it is the 32-bit or 64-bit version.

Open the Correct ODBC Administrator

Search your Windows Start menu for 'ODBC Data Sources'. Select either the 32-bit or 64-bit version to match your Microsoft Access installation.

Configure the Working Oracle Driver

Under the System DSN or User DSN tab, verify that your connection utilizes the Oracle client driver that is known to work for this environment.

Delete and Recreate Access Links

Open your Access database, delete all existing linked tables pointing to the Oracle database, and then use External Data > New Data Source > From Database > From SQL Server (or ODBC Database) to recreate the links using the newly verified DSN.

Architecture Mismatch Warning: If you are running 32-bit Access on a 64-bit Windows machine, you must strictly use the 32-bit ODBC Data Source Administrator (located at C:\Windows\SysWOW64\odbcad32.exe) and a 32-bit Oracle client.

Solution 2

Resolve Multiple Oracle Client Conflicts

Check for and resolve conflicting Oracle client installations and authentication configurations that might interrupt credential retrieval.

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Frequently Asked Questions

What causes the ORA-12638 error in Microsoft Access?

This error typically occurs due to architecture mismatches (e.g., using a 64-bit ODBC driver with 32-bit Access) or authentication conflicts in environments where multiple Oracle clients are installed.

How do I know if I should use the 32-bit or 64-bit ODBC administrator?

The ODBC administrator must match the architecture of your Microsoft Access application, not necessarily your Windows OS. Check your Access version under File > Account > About Access.

Why does another application like LinqPad connect but Access fails?

LinqPad and similar applications might be running under a different architecture (e.g., 64-bit while Access is 32-bit) or using native providers rather than the specific ODBC driver setup that is failing for Access.

Will recreating linked tables delete my database data?

No, deleting and recreating linked tables in Microsoft Access only removes the connection reference to the Oracle database. The actual data stored within Oracle remains completely unaffected.

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