Basic Framework of Job Control Language-JCL

My head’s spinning around the 3 JCL Statements : JOB, EXEC and DD. Could you tell me something more about them?
So, you’ve got the gist of the concept behind JCL, all the JCL that you going to write from hereon, maybe for the next 10-20 years, would be composed of three main statements :

//name	JOB	parameters...
//name	EXEC	parameters...
//name	DD	parameters..

Each of this JCL Statements have a label – a symbolic name assigned to them. Its like naming kids. Well, there could be so many boys in your area, but how do distinguish them? Of course, by their names.


In the same way, a JCL may contain a bunch of DD Statements, one for Input file, one for the output file, one for the error file. How do you tell them apart, by naming them. As a good practice, we always give names to all our JCL Statements. Names kinda help you to refer back to these statements in the future. You want to point out a particular JCL Statement to your friend, just spell out its name.

But, notice carefully, each label(name) is preceded with two slashes //. The two slashes are a JCL Statement’s signature. They indicate that the statement is a JCL Statement(one of JOB, EXEC, DD). Every JCL Statement wear the two slashes //. A naked statement without // won’t be treated as a JCL Statement.

Now, every JOB, EXEC and DD Statement has got these whole lot of parameters. What you’ll be learning throughout these tutorials is mostly the parameters. Parameters add stuff and meaning to the JCL Statement.

Now, let me give you a booster, that’s going to help you organise the way you think about this JCL.

JCL is made up of mainly JOB, EXEC and DD.
- JOB is easy to learn and use.
- EXEC is easy and fun to use.
- DD Statements take three forms
   1. DD Statements to read a file.(easy)
   2. DD Statements to write to the logs.(easy)
   3. DD Statements to create a new file(hard!); you’d have to learn parameters such as DISP, UNIT, DCB, SPACE and several others to code this.

Have a good look at this chart :

Oracle buying Sun will change the IT industry

1) MySQL is dead. Long live MySQL. Oracle doesn't have much to say about MySQL. Why should they? They're going to quietly kill the open-source DBMS as fast as possible.

Unfortunately for Oracle, it's too late. MySQL, under Sun's mismanagement, had already forked. MySQL founder, Michael 'Monty' Widenius left Sun and started his own community branch of MySQL, MariaDB. His purpose? "To provide a community developed, stable, and always Free branch of MySQL that is, on the user level, compatible with the main version."

That's one of the things that Ellison, and Microsoft for that matter, don't get. You can't kill open-source projects. Companies come and go, but popular open-source programs like MySQL just keep rolling on.

2) Solaris/OpenSolaris. Oracle is making sounds like it wants to do something with Solaris. Just don't ask me what. Solaris has been declining for years. Oracle uses Linux internally, and it even has its own rip-off of RHEL (Red Hat Enterprise Linux), Oracle Unbreakable Linux.

Ellison can talk all he wants about Sun's Solaris operating system being "by far the best Unix technology," but so what? Unix is dying. Linux has been eating away at the Unix market for more than a decade. Ellison's support of Unix makes a good sound-bite, but as a business move it makes no sense. I predict death by neglect for Solaris.

3) Java. Java has value, but Sun's done a poor job over the years of turning that value into money. Oracle, which uses Java in many of its applications, can certainly put Java to good work in supporting its own products. My question is, "What is Oracle going to do with the Java Community and vice-versa?"

I know some things will happen. NetBeans, for example, is history. Oracle is a big-time Eclipse supporter. As for the rest? I honestly don't know what Oracle will do with the JCP (Java Community Process). If they're smart, they'll get everyone together as soon as possible to spell out their future plans for Java. If Oracle doesn't, they'll have Java developers running, not walking, away from the Sun/Oracle Java as fast as they can.

4) SPARC. Oracle can talk all it wants about taking a step back to the past where companies sell hardware and software bundles, but I don't see it. Fujitsu will continue to make SPARC boxes for that dwindling market, and I expect to see Sun's x86-server based business getting either spun out as an independent company or sold to Dell or HP. I just can't see Oracle in the hardware business.

5) Sun's other open-source programs. I have a bad, bad feeling that Oracle is going to let popular and powerful open-source projects like OpenOffice and VirtualBox wither on the vine. Oracle is willing to spend money on open-source projects that it uses. For example, Oracle is a top contributor to ldLinux. But, I don't see these, or Sun's other open-source projects, contributing to Oracle's bottom-line, so I don't see them getting much support.

Over the years, Sun has contributed, albeit reluctantly at times, many great advances in operating systems and open-source software. With this acquisition, those days are done. Good-bye Sun, it was nice to have known you.
Courtesy:ComputerWorld