2.2 Installing Perl DBI

Now that you've installed Perl itself, you need to set things up so your Perl programs can communicate with your Oracle database. The best way to do this is via the magic of the Perl DBI module and its Oracle-specific database driver, DBD::Oracle. These modules let us gain access to our target database through the Oracle Call Interface provided by Oracle Corporation. The architecture for this arrangement, which takes full advantage of the object-oriented features available within Perl 5, is shown in Figure 2-2. This figure also demonstrates how the same Perl DBI interface can be used, with other drivers, to connect to other databases, and how all of these drivers are hidden from your Perl scripts by the DBI package.^[1]

^[1] You can even access different database types within the same Perl script using DBI. Doing so can be especially useful when you want to transfer information from one database type to another without having to use Oracle's SQL*Loader product.

This section focuses on the installation of Perl DBI. For more information about Perl DBI's capabilities, see Appendix B, and the book and online references listed in Chapter 1. For complete online information, go to http://dbi.perl.org.

We'll show how to install the DBI modules for both Unix and Win32.

Figure 2-2. The Perl DBI architecture

Before we get to the DBI and DBD::Oracle modules, however, we need to take a step back to discuss the methodology we'll be using for installing Perl modules onto Unix systems, both here and in the rest of the book.

2.2.1 Methods for Installing Perl Modules

There are two basic approaches to installing Perl modules (for example, Perl DBI, DBD::Oracle, and the many other modules we'll be discussing in later chapters) on Unix systems. The first is what some people call the traditional method. The second is the CPAN method. We recommend the traditional method, as we describe in the next section, but because the CPAN method is quite popular, we'll describe that one here as well.

2.2.1.1 The traditional method

Briefly, the traditional method consists of the following steps:

This process often requires specifying the following steps on the command line (once the module tarball has been downloaded from the CPAN site, http://www.cpan.org ).

$ gzip SomeModule-1.00.tar.gz  # Unzip archive
$ tar xvf SomeModule-1.00.tar  # Unpack archive
$ cd SomeModule-1.00           # Enter archive
$ perl Makefile.PL             # Configure the build
$ make                         # Build, or compile, the module
$ make test                    # Test the module's compilation
$ make install                 # Install the tested module

There are a lot of keystrokes here. However, there is a way to cut down on this effort, and that's to use the CPAN module described in the next section.

2.2.1.2 The CPAN method

The CPAN module (a separate entity from CPAN itself) provides a streamlined way to install Perl modules. You can learn the details of this built-in module by running the following commands:^[2]

^[2] The perldoc (Perl documentation) program itself is installed automatically with Perl, as part of the general Perl development environment.

$ perldoc perlmodinstall
$ perldoc CPAN

If you have a valid Internet connection open, you will have two ways of using CPAN. You can use either an interactive shell or a direct command-line instruction. We'll load up two modules in the following sections using these methods.

The CPAN module comes prebundled with Perl. When you run its shell (described in the next section) for the first time, it will ask you a one-time series of short configuration questions. Once you've completed these, you're ready to start installing online!

2.2.1.3 The interactive CPAN shell

First, we'll try the interactive CPAN shell, and install Number::Format, a helpful Perl module for manipulating number and string displays, particularly financial data:

2.2.1.4 CPAN from the command line

Using CPAN directly from the command line is even easier than using the interactive CPAN shell. We'll use it to get another useful Perl module, the Convert::EBCDIC bundle, which deals with IBM mainframe EBCDIC data and its conversion to and from ASCII formats. Follow these steps:

2.2.1.5 The traditional method

As you can see, the CPAN installation method is very convenient. However, like many Perl developers, we've chosen to use the older paradigm because it gives us better control and is more reliable.

Many of the modules we're going to discuss in this book have compilation routes that deviate from the norm. CPAN is a fire-and-forget missile. You press the button, and away it goes, but it always expects our target to be in view. If the target is elsewhere, it's intelligent enough to try to adapt, but it may still fail to do exactly what you wish, and consequently miss the mark. On the other hand, because of the greater number of steps required by the traditional method, we actually achieve better granularity when we use that method, and we find it particularly helpful when explaining Perl to others. We can hop between steps and offer you more advice on debugging, alternative location installations, and other compilation tips (particularly in places where the Perl module is a glue layer camouflaging the more difficult API of a passenger C library, which itself needs compilation).^[3]

^[3] You can think of the difference between the CPAN and traditional methods as analogous to the old conflict between what's called, in military circles, Sigint (Signals Intelligence) and Humint (Human Intelligence). Sigint, or CPAN, is easier to deploy and gather information from, whereas the traditional cloak-and-dagger Humint, pays for its greater management overhead with a greater depth of penetration.

Thus, from here on, we're going to sidestep the CPAN module and stick mainly to la methode traditionelle as we discuss Perl installation. However, if you ever get jealous of Win32 people using PPM (the Perl Package Manager, which we describe in the later section, Section 2.2.3), nothing stops from you using CPAN; we promise to turn a blind eye, especially as we use PPM quite often.

2.2.2 Installing Perl DBI on Unix

In this section, we'll explain how to install Perl DBI using the following tarballs:

DBI-1.20.tar.gz

DBD-Oracle-1.12.tar.gz

The central locations for these are:

http://www.perl.com/CPAN/modules/by-module/DBI

http://www.perl.com/CPAN/modules/by-module/DBD

You can obtain the relevant interface and driver packages by clicking on and saving the files from the appropriate links. Save them to a Perl module repository.

2.2.2.1 Installing Perl DBI

Once you have the relevant downloads, you can begin the Perl DBI installation. Before starting, always scan through the relevant README files; the following instructions do change gradually over time. If any problems occur with your installation, you'll find that the solution is most likely buried deep within either the DBI or the DBD::Oracle README files. Follow these steps:

Perl DBI should now be installed. But we need to keep the bubbly on ice, for a little while longer. The next stage is to pair DBI up with its partner, the DBD::Oracle driver.

2.2.2.2 Installing DBD::Oracle

Follow these steps to install the DBD::Oracle module:

If you can't solve your problem (which should be a very rare case), you may be able to get help from the DBI users mailing lists or from the helpful information in the DBI FAQs. We explain how to access these at the end of Chapter 1.

Once you've successfully completed the make install step, you'll find plenty of up-to-date Perl DBI documentation automatically loaded onto your system. You can ensure that the documentation has been loaded by running the following pair of commands:

$ perldoc DBD::Oracle
$ perldoc DBI

2.2.3 Installing Perl DBI on Win32

In contrast to the Unix installation, installing Perl DBI using ActiveState's version of Perl is very straightforward. We recommend that for Win32 you use the PPM (Perl Package Manager) module, which installs automatically alongside ActivePerl with its utility ppm program (which runs it).

PPM simplifies the tasks of locating, installing, upgrading, and removing software packages on Win32. It determines whether the most recent version of a software package is installed, and can install or upgrade that package from a local or remote host. PPM is very similar to the interactive CPAN shell module described earlier. Although PPM is usually run via its ppm interactive shell program, it can also be used directly on the command line. PPM uses PPD (Perl Package Description) files containing an extended form of the Open Software Description specification,^[6] for information about software packages. These description files are written in XML. For more information on PPM on Win32, run the very helpful perldoc command; we'll say more about perldoc in Appendix A:

^[6] http://www.w3.org/TR/NOTE-OSD.html

DOS> perldoc PPM

We've chosen to use PPM ActivePerl packages, instead of hand-crafting Perl module installations, for the following reasons:

• Most Win32 users don't have a development environment in which to compile and test source code installations.

• Many Perl modules on Unix require the manual compilation of libraries such as zlib for compression, expat for XML parsing, or gd for dynamic image creation. All ActivePerl modules have precompiled these libraries for you into DLLs, where necessary, before you download them. These will save you a significant amount of work over compiling DLLs of your own.

• Just as compiling from source is the standard method for installing Perl on Unix, the de facto standard method on Win32 is to use PPM.

2.2.3.1 Running PPM

For a comprehensive guide to installing Perl modules on Win32, check out the following site:

http://aspn.activestate.com/ASPN/Products/ActivePerl/faq/ActivePerl-faq2.html

Unless you're accessing the Internet through proxies, as we'll discuss shortly, the following steps should take only a few minutes:

2.2.3.2 Getting the latest PPD files

For the very latest Perl DBI and DBD::Oracle packages on Win32, you can go beyond ActiveState and turn to a knight in shining armor, Ilya Sterin. Ilya regularly provides the latest binary compilations at the http://xmlproj.com/PPM web page. Check this site first! If the PPD files you're looking for are there, you can run the following PPM commands to obtain the very latest DBI and DBD::Oracle downloads:

DOS> ppm
PPM> remove DBD::Oracle
PPM> remove DBI
PPM> set repository XMLPROJ http://xmlproj.com/PPM/
PPM> install DBI-1_20
PPM> install DBD-Oracle-1_12
PPM> quit