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Old 10-22-2014, 08:50 AM   #1
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Lightbulb MSSQLServer Linked Server to Oracle - Strange Behavior after updating SQL settings

Started a question. Got it working. This is now for the benefit of somone else using an Access Linked table to SQL Server view that consumes an Oracle DB using Linked Servers. (Does that count as a run-on sentence?)

The Access database has a DSN-Less Linked table to MSSQLServer for a query based on a Linked Server to Oracle. This requires the Oracle Client OLE DB ODBC driver. (See attachment). The attachment doesn't show the Access linked table. The view in SQL Server uses the Cast to change Oracle Text over to Integers or other data types.

This was all working fine until the IT dept notified me that the Oracle host was moved over a weekend. The UN/PW was also changed.
- Go into TNSName.ORA and edit the reference (see example below).
- Go to Linked Server in SQL and update the UN/PW

A link to one of three test DB worked perfectlly.
The links to production (and two other test) had an error. Error:
Can't Caculate a text field.

This is strange because all 4 instance of the SQL Server Databases are in one SQL Server. They all point to the exact same instance of a Linked Server. That is, a table in each SQL Server DB have the same view that consumes a Oracle Linked Server's table. (see the attachment)

It is stranger because even down to the Linked Table of Access, the Linked Table def had the header information and data types.
Just no data on the Production DB using the same linked table
While the Test DB using the same linked table had connection and the data.

The Test DB was a restored backup of the production DB.
A second Test DB behaved like the production - no data.

The lack of data was at the SQL Server view.
- Dropped and recreated linked table from Access - no change
- Scripted and created a 2nd SQL Server view - it behaved as the orginal view on production. The test 2nd view showed data as its parent did.
- Dropped and recreated the view of the linked table. No change.

Solution: About 5:30 PM, fustrated, took a 10 minute walk around downtown making a decision if to stop at the Tilted Kilt for a drink.
Returned to office at 5:30 to go through all steps again.
Clicked on the Access linked table to start at end documenting each error.
The production copy worked perfectlly! I didn't do a thing except stop using SQL Server Enterprise Manager for troubleshooting.
Has been working all night and all day now.

The 3rd Test DB on SQL Server this morning still had the exact same Linked Server error. Put that 3rd SQL Test dB into single user mode, stopped service, restarted. The Linked Server data worked perfectlly.
I started the question but now things are working.

Final Solution:
For anyone using SQL Server Linked Servers, Stop and restart the Database consuming the Linked Server before spending hours assuming something is wrong.
Had I stopped and restarted the entire SQL Server, all the DB would have probably refreshed. This indicates a property change in Linked Servers may not replicate across all SQL Server DB equally.

A TNSName.ORA file will resemble this:
Another very useful Blog: http://oraclequirks.blogspot.com/
This site is: "Annals of Oracle's Improbable Errors"
Attached Images
File Type: jpg Concept of SQL Server Linked Server to Oracle.jpg (71.3 KB, 99 views)

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Last edited by Rx_; 10-22-2014 at 09:13 AM.
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linked server , odbc , oracle , sql server

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