Even am looking out for the answer....Can anybody answer?
The person who answers this question is a brilliant person i
suppose!!!

Mainframe is technology...like we have JAVA,C++etc...For 
mainframes we have COBOL as Langauge,JCL (Job Control 
Language),DB2 Database is used.
Mainframes Testing is nothing but to test a program of 
mainframe, which would be written in COBOL,will run with 
the help of JCL and will be using DB2 database.
Please correct me if I m wrong.

For mainframe testing HE/SHE should be aware of the 
navigations in mainframe application(ISPF).
The testing process would be same as other applications.
We may need to work on mainframe applications 
like ....COBOL,JCL,VSAM and DB2
It would be good if you know the utilities like FILE-
AID,CHANGEMAN and XPEDITER

On the performance aspect

# you can 'benchmark' DB2 server.

# COBOL coding techniques etc..

Hi Friends I workied in Mainframe project in 1 year 3 
months. I am sharing my experience with you all.

first of all we now navigation of the application in the 
mainframes.

I did tested the insurance project in mainframe project,

after promotion of the code, we will set the parameter file
(this is not required for all projects,its based on 
projects).

then i will do some transactions or modifications based on 
the requirements. then I will request the supporting team 
to run the Jobs.

after running the jobs, I will check the DB2 tables and 
where I am expecting the expected results. If all working 
fine then Ok.Other wise there is a defect.