DBA Tips Archive for Oracle
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by Michael New, MichaelNew@earthlink.net, Gradation LLC
Oracle started support for making external procedure calls from PL/SQL code in Oracle8. An example would be a PL/SQL program calling one or more C routines that are required to perform special-purpose processing. This option remained practically unchanged until Oracle9i (9.2.0).
In version 9.2.0, Oracle decided it was time to tighten up security and make several modifications to this feature. It wasn't until I tried to run several C routines under 9.2.0 that I came up with the following error:
I finally broke down and starting reading over the Oracle9i Net Services Administrator's Guide Release 2 (9.2) and found the answer as to why this was not working.
This article simply explains some of the changes made in 9.2.0 and what changes you will need to make to your environment to call external procedures.
For a detailed overview on configuring PL/SQL to call external procedures, take a look at my article, "Calling OS Commands from PL/SQL using External Procedures".
In short, Oracle changed the default behavior in 9.2.0 to disallow
any external procedure other than those in
%ORACLE_HOME%\bin (for Windows)
$ORACLE_HOME/lib (for UNIX).
You can use external procedures in other directories, but you have to add an environment variable called EXTPROC_DLLS to your listener.ora. This environment variable will contain the names of the DDLs (delimited by a colon) that you wish Oracle to have access to.
You will not
need to make any modifications to your tnsnames.ora entry for the
In the case of my development machines, I can set the "ANY" option - meaning my external procedure can be in any DLL in any part of the file system.
In a production environment, you may want to allow DDLs to be loaded
not just from
but also allow specific DDLs in other directories.
The example below
will allow DDL loads from
and the DDL
To achieve a higher level of security in a production environment,
you may want to restrict the DLLs that the extproc agent can load
by listing them explicitly in the
listener.ora file with the ONLY
In this configuration, Oracle will only load the DDLs listed. It WILL NOT
%ORACLE_HOME%\bin (Windows). The example below
will ONLY be able to load
Jeffrey Hunter is an Oracle Certified Professional, Java Development Certified Professional, Author, and an Oracle ACE. Jeff currently works as a Senior Database Administrator for The DBA Zone, Inc. located in Pittsburgh, Pennsylvania. His work includes advanced performance tuning, Java and PL/SQL programming, developing high availability solutions, capacity planning, database security, and physical / logical database design in a UNIX / Linux server environment. Jeff's other interests include mathematical encryption theory, tutoring advanced mathematics, programming language processors (compilers and interpreters) in Java and C, LDAP, writing web-based database administration tools, and of course Linux. He has been a Sr. Database Administrator and Software Engineer for over 20 years and maintains his own website site at: http://www.iDevelopment.info. Jeff graduated from Stanislaus State University in Turlock, California, with a Bachelor's degree in Computer Science and Mathematics.
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Last modified on
Sunday, 18-Mar-2012 22:29:32 EDT
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