There are basically 2 types of PROCS, a. Instream, b. 
Cataloged. 

The Nesting of procs is not possible.

Hi, A Proc is nothing but it can be a set of Program which 
is utilised by the Main JCL.It's basically used for 
avoiding the number of lines of coding the JCL statements 
in the main JCL and we can call the Proc's when ever needed 
for performing a certain kind of action. 

There are 2 types of Proc's and they are Instream & Catalog 
proc. 

The nesting in Procs are possible and the maximum number of 
levels are 15 levels.

Hi Ram,

Could you please provide with some example of nesting in 
Procs (both instream and cataloged)

Hi,
 what they said is correct but nesting procs is not 
possible in proc

when we want use some part of prog in many prog we store in 
proc

In-stream procs can be nested upto a maximum of 15 levels
(we can not make a backward reference in nested procs).

Can some one of u justify wid examples?

this is generaly avoided to use nesting proc , because it 
make job complex to understand,and this use only in catalog 
proc.if you want to use then nesting is possible up to 15 
level.