MacLochlainns Weblog

I left to chance where students would attempt to place their external files in a Linux or Unix implementation. As frequently occurs, they choose a location in their student user’s home directory. Any attempt to read an external table based on a file in this type of directory fails because it’s not accessible by the Oracle user because the directory within the student user’s account isn’t reachable. You can’t simply chown a directory and the files in a directory.

The failure returns the following result:

SELECT COUNT(*) FROM transaction_upload
*
ERROR AT line 1:
ORA-29913: error IN executing ODCIEXTTABLEOPEN callout
ORA-29400: data cartridge error
error opening FILE /home/student/upload/transaction_upload.LOG

The reason isn’t readily visible to all, but a virtual directory must reference a physical directory owned by the oracle user and dba group. That also means the oracle user must own all directories from the logical mount point to the physical directory name.

Assuming you’re working in an Oracle Database 11g XE instance, you can create a valid upload directory by navigating to this directory:

/u01/app/oracle

Then, issue this command as the root user to create a new upload directory:

mkdir upload

Now you have the following directory:

/u01/app/oracle/upload

Assuming you’ve created the upload directory as the root user, the root user should issue the following two commands from the /u01/app/oracle directory:

chown -R oracle:dba upload
chmod -R 755 upload

Having made that change you should now be able to query the external file source, like a *.csv (comma-separated values) file. Hope this helps those trying to use external tables, which I subsequently wrote about for Toad World – External Tables.