DBA Tips Archive for SQL Server
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by Jeff Hunter, Sr. Database Administrator
If you are a system administrator or DBA, you know the importance of scripting. For most administrators, the choice is Perl. Given the fact that Perl is open source, available on almost all O/S platforms and extremely modular, many popular modules have been developed to extend the language. DBAs for example, have enjoyed the ease of scripting database functions using the "Database independent interface for Perl" or better known as DBI.
The DBI is a database access module for the Perl programming language. It defines a set of methods, variables, and conventions that provide a consistent database interface, independent of the actual database being used.
Using the Perl DBI interface, you must first download and install the mandatory DBI Perl module. Downloading and installing all Perl modules mentioned in this article will be discussed in later sections.
At the time of this writing, the most current release of DBI available from CPAN.org is version DBI-1.614.
After installing DBI, you then would download and install any of the available DBD Perl modules (database dependent modules) that correspond to the database you would like to connect to and work with. Many DBD modules exist today for popular databases like Oracle, MySQL, Sybase as well as access other alternative data sources like CSV, Excel, and even Google! Like the Perl DBI module, you can find a comprehensive list of available DBD Perl modules at CPAN.org.
Looking at the list of available DBD modules on CPAN, you may have noticed one missing from the list - Microsoft SQL Server 2000!
This article will focus on how to access Microsoft SQL Server 2000 from a Linux server using the Perl DBD::Sybase driver module (this is the Sybase driver for the Perl DBI) combined with FreeTDS. FreeTDS is a set of libraries for Unix and Linux that allows your programs to natively talk to Microsoft SQL Server 2000 and Sybase databases.
Having this type of access presents more options to DBAs scripting in Perl as well as web developers using CGI scripts since they can now access MS SQL Server 2000 in the same manner they would access any other DBI support RDBMS server.
All testing done for this article was performed using the following software components:
CentOS 4.2 Enterprise Linux Operating System
CentOS is a stable clone of the actual Red Hat Enterprise Linux operating system.
Several of the software components in this article will need to be compiled from source code. Red Hat conveniently installs GCC, the GNU C compiler and is installed by default on most Linux platforms.
I am using the same exact Perl installation that comes installed by default with CentOS or RHEL - "v5.8.5 built for i386-linux-thread-multi".
Instructions for downloading and installing the Perl DBI module is provided later in this article.
Instructions for downloading and installing the Perl DBD driver module for Sybase is provided later in this article.
FreeTDS - (freetds-0.63)
Instructions for downloading and installing the FreeTDS source code is provided later in this article.
This article applies to scripts running on the Linux/UNIX operating environment. If you have Perl scripts that are running on Microsoft Windows, you can simply use the DBD::ADO driver module for accessing SQL Server.
Designed and developed by Sybase Inc. in 1984, Tabular Data Stream (TDS) is a protocol used to support network communications for their SQL Server relational database product. Like many companies during this era, Sybase faced a problem with the fact that no commonly accepted application-level protocol existed to transfer data between the client and the database server. In hopes to encourage use of their product offerings, Sybase developed a pair of libraries named netlib and db-lib.
Note that a protocol is not an API. The two, however, are related. A protocol is when two computers have the ability to speak the same language. A server, for example, will be able to recognize and respond to a client request that has the right combination of bits in the correct order. This is all the responsibility of a software library. Today, many software libraries exist and they all have their own API. With regards to our current discussion, they are responsible for moving SQL data through a TDS pipe. Although ODBC, db-lib, ct-lib and JDBC have very dissimilar APIs, they are all considered the same to the server because on the wire, they speak TDS. For example, ODBC, db-lib, ct-lib and JDBC differ dramatically in their programming style and convention but they all use netlib to communicate to the server. The language they all use is TDS.
Netlib was responsible for the transport of data between two computers and can run on IPX/SPX, DECnet, NetBEUI and the ubiquitous TCP/IP. Db-lib, on the other hand, provided the API to the client program and did all of its communication with the server via netlib. Whatever db-lib sent to the server took the form of a stream of bytes (actually, a structured stream of bytes meant for tables) and was called a Tabular Data Stream.
Thanks to a technology sharing agreement with Sybase in 1990, Microsoft starting marketing its own SQL Server. All Microsoft SQL Server products then made use of the same network communications protocol used by Sybase - TDS.
Within the technology sharing agreement with Sybase, Microsoft's SQL server products were being developed with the same network communications protocol that Sybase used, namely TDS. Through the release of SQL Server 7.0, Microsoft officially supported Sybase client software with a caveat that such support would come to an end. Until SQL Server 2000, is was then possible to use the Perl DBD::Sybase module (compiled with Sybase's freely downloadable client libraries) to access any Microsoft SQL server!
With the introduction of TDS 8.0 and now legacy support for TDS 7.0 in SQL Server 2000, compatibility with the Sybase client, using TDS 4.2, is broken. There is a work around however to accessing SQL Server 2000 and this article describes how!
The crux of this article is how to access Microsoft SQL Server 2000 using the DBD::Sybase Perl module built with the TDS libraries (FreeTDS) from freetds.org which do support TDS version 7.0
Let's now start by downloading the required software components. As I mentioned in the introduction to this article, I am utilizing the CentOS 4.2 Enterprise Linux operating system (a free and stable RHEL clone). During the Linux installation, I made sure to install Perl and the GNU C compiler. Both Perl and the GNU C compiler are available in RPM format from the Red Hat CDs. This article does not discuss installing the Linux O/S, Perl or the GNU C compiler.
The following is a list of software components / modules that should be downloaded. Instructions for unpacking, installing, and configuring these modules are discussed later on in this article.
Perl DBI Module
Perl DBD::Sybase Module
The first component to install (if it is not already installed) is the Perl DBI module.
Use the following commands to unpack, build and install the Perl DBI module. Please keep in mind that the all of the following commands can be performed as any UNIX user, however, the make install must be performed as root.
The next step is to unpack, configure, build and install FreeTDS.
Note that when running configure, we need to use the --with-tdsver=7.0 in order to create a Makefile suitable for compiling FreeTDS that specifies TDS 7.0 as the default protocol. Also note that I choose to install FreeTDS to /usr/local/freetds using the --prefix=(PATH) option.
The final component to install is the Perl DBD::Sybase driver module. The commands used to install the DBD::Sybase driver module are exactly the same as building the Perl DBI module. There is on extremely important exception and that is that the environment variable SYBASE MUST be set to the path of the FreeTDS installation prior to installing DBD::Sybase.
Before configuring and installing the DBD::Sybase driver module, ensure to set the environment variable SYBASE to the path of the FreeTDS installation. In this article, we used /usr/local/freetds.
If your shell is BASH or KSH, use:
Although, not important for the installation phase, you should also set your LD_LIBRARY_PATH environment variable to the /lib directory as in:
Both of these environment variables should be set your login profile (i.e. .bash_profile)
See http://www.freetds.org/userguide/envvar.htm for further information on setting environment variables for FreeTDS.
Use the following commands to unpack, build and install the Perl DBD::Sybase driver module. Please keep in mind that the all of the following commands can be performed as any UNIX user, however, the make install must be performed as root.
Also note that the Makefile.PL script asks you for information about your Sybase server. It uses this information to build and write a file called PWD which is used by the test utilities provided with the module. These tests were designed to run against a Sybase server - not Microsoft SQL Server 2000. Keep in mind that any error messages indicating No library found are due to compiling DBD::Sybase with the FreeTDS libraries instead of Sybase's and can be safely ignored.
At this point, all software components and modules are installed. The final step is to configure FreeTDS to talk to your SQL Server 2000 database!
FreeTDS uses a configuration file called freetds.conf. This file can be found in the FreeDS installation directory under /etc. In this article, the file would be located at /usr/local/freetds/etc/freetds.conf. This file contains several configuration examples (some commented out) and it is very possible to modify one of them to reflect your server's information.
Here is an example entry I made:
The name of my SQL Server in the above example is melody.idevelopment.info and is running its database service on the default port of 1433. Notice that I have also specified the tds version of 8.0.
Now let's take a look at our new configuration in action by running a couple of example Perl scripts.
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
Wednesday, 28-Dec-2011 14:05:13 EST
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