17.1 Where can you find applications for Linux on the mainframe?

It is not difficult to find applications for Linux on the mainframe. Here are some sources:

• Applications that come with your Linux distribution

• Open Source applications that are not shipped by distributors

• Commercial applications from independent software vendors

The following sections cover general considerations for sources of applications. For specific examples of Linux-on-the-mainframe applications, see Chapter 27, "Examples for Applications."

17.1.1 What comes with a distribution?

While some companies might have the skill to build their own Linux systems, most of them turn to commercial Linux distributions as the source for well-defined and stable foundations for their production systems. Distributions for Linux on the mainframe, like all major Linux distributions, contain hundreds of program packages.

The large number of available Linux applications and the broad spectrum of user requirements make it impossible for a single distribution to serve all needs. Many of the applications included in distributions, therefore, serve general needs that are common to most IT installations, and you are likely to find an interesting set of applications that is useful to you.

All current mainframe distributions include Samba for file and print serving, Sendmail for e-mail services, Apache and Tomcat for Web serving, MySQL as a database server, Network File System (NFS) for file serving, openLDAP for directory access, and openSSL for implementing secure connections.

Typically, distributions also include tools that help you to manage the applications on your Linux system. These tools cover, for example, installation, packaging, problem management, and version control. In addition, there are some basic utilities such as editors, compilers, and debuggers that you might need for porting or developing code on Linux.

A distributor assures the compatibility of the software packages within a distribution. Hence, you do not need to worry about the compatibility of an included application with the Linux kernel and the interoperability of included applications. Applications from your distribution are available on the installation medium. The distribution might also provide service and maintenance support for the applications.

17.1.2 Open Source applications

The Internet offers a spectrum of applications that goes far beyond what any distribution may offer. The following three Web sites are good starting points for finding Open Source applications:

• http://www.linux.org/

• http://sourceforge.net/

• http://freshmeat.net/

With Open Source applications that are not included in a distribution, it is up to you to ensure the compatibility with your base Linux system and any other software you run on it.

Open Source applications are maintained by the Open Source community. Usually, there are no contractual guarantees of service and accountability. Often, this lack of contractual commitments is an inhibitor to businesses for deploying Open Source applications from the Internet in mission-critical functions. In response to that, commercial versions have been provided for some of the Open Source software. For example, for Samba and MySQL there are commercial versions as well as Open Source versions available under the GPL license.

The value of obtaining Open Source applications from the Internet is the great degree of choice and freedom it gives you, including the option to modify the code, and the low cost of acquisition. If you are looking for an application to cover very specific requirements in your installation, you are likely to find Open Source code that you can tailor to your needs.

17.1.3 Commercial applications

Many useful applications for Linux on the mainframe are commercial applications. These applications are usually subject to regular release cycles, which means better predictability in planning your systems.

For information on the commercial IBM software that is available for Linux on the mainframe visit:

http://www.ibm.com/software/is/mp/linux/software/

IBM maintains a separate site with information on the hundreds of commercial program packages for Linux on the mainframe that are offered by other independent software vendors:

http://www.ibm.com/servers/eserver/zseries/solutions/s39da/linuxproduct.html

With commercial applications, you incur license fees and you might also incur dependencies on supporting software, specific distributions, and release cycles. What you gain is maintenance and service support for the product.

17.1.4 What if the application you want is not available?

If an existing application you want to run is not available for Linux on the mainframe, you might want to ask its provider if a port is planned in the near future and register your requirement for such a port.

You might also want to check for alternative applications. There might be suitable solutions available that are already supported. Moving applications to Linux on the mainframe is an opportunity to upgrade the technologies you are using. Linux applications generally have a reputation for being up to date on new standards.

You might also have your own proprietary applications that you want to bring to Linux on the mainframe (see Chapter 18, "Porting Applications to Linux on the Mainframe").