This page serves as a basic guide to the MVS operating system. UCC is running an MVS system on Macropoma using the Hercules emulator which emulates IBM mainframe architectures.

== History== First released in 1974, Multiple Virtual Storage (MVS) was an operating system designed to run on IBM system/370 architecture mainframes. MVS was developed as a successor to OS/360 and existed in several significant versions. It would later be renamed to OS/390 in 1995 and then eventually to z/OS which is the current dominant OS run on IBM mainframes.

MVS was initially released as a free product, however it was later bundled with several other IBM products at which point IBM changed the the license and started charging a license fee. Version 3.8j being the last free release is generally considered to be in the public domain and is the last release that can be legally run without seeking a license from IBM. Unfortunately many of the programs that are commonly used on MVS and z/OS systems, such as ISPF, SDSF, and CICS are not freely available and cannot be run on our system.

== Technical Background== MVS 3.8 is a 24-bit operating system and was written almost entirely in Assembly. Later versions were adapted to support 31-bit then 64-bit (z/OS) addressing.

MVS supports a range of different peripheral devices. Under MVS there are two main types of storage device. A direct-access storage device (DASD) is any secondary storage where each physical data record has a discrete location and unique address allowing the system to random access the data on the device. This term encompasses devices such as hard disk drives and magnetic drums.

In contrast to DASD's are Sequential access devices such as tape drives and punch card readers and writers. Sequential devices are the primary method to used to transfer data onto and off of mainframes. Hercules has been configured to emulate these devices by writing to and reading from files on the host.

Operator interaction occurs primarily through 3270 terminals or 3215 printer-keyboard combinations. 3270's were originally physical terminals, however RFC1576 outlines methods for a server to translate 3270 data streams into a telnet stream, allowing telnet based 3270 emulators to connect to mainframe hosts. Hercules emulates the 3270 devices for us and presents them via telnet3270 (tn3270).

VMS and its successors use the EBCDIC codepage, this means text files will need to be converted when transferred to and from the mainframe.


Mainframe terminology can often be fairly cryptic some common terms include:




Time Sharing Option, a multi-user shell environment


A group of bytes, In text datasets 1 record = 1 line


A dataset is collection of records, equivalent to a file


Alternate term for a record, A card is normally a fixed size of 80 bytes


direct-access storage device

Job card

The first card of a JCL dataset

How to Use MVS


Connect a tn3270 client to Macropoma, using x3270 this would be achieved with x3270 macropoma:3270.

The 3270 is a block orientated terminal, this means that anything you type is on the screen is stored locally and is only submitted to the server when you hit enter.

Afer connecting you should be presented with the UCC welcome screen, if you do not see this screen you can hit the CLEAR key to refresh the screen. Type your userid after the logon prompt and hit enter.

Terminal   CUU0C0                                                 Date  05.05.20
                                  WELCOME TO THE                  Time  12:27:30
                          UUU    UUU    CCCCCCCC     CCCCCCCC                   
                         UUU    UUU   CCC    CCC   CCC    CCC                   
                        UUU    UUU   CCC          CCC                           
                       UUU    UUU   CCC          CCC                            
                      UUU    UUU   CCC          CCC                             
                     UUU    UUU   CCC    CCC   CCC    CCC                       
                     UUUUUUUU     CCCCCCCC     CCCCCCCC                         
      This is Macropoma at The University of WA - for authorised users only     
                              ***  WARNING  ***                                 
        Misuse of computer access can attract criminal penalties, civil         
        liability for third party loss and university disciplinary action.      
                      This system is running TK4- based on                      
                              MVS 3.8j Level 8505                               
Logon ===> coffee                                                                     
                                                            RUNNING  TK4-       

You will be prompted to enter your password. If you wish to change your password you can enter OLDPASSWORD/NEWPASSWORD at this prompt. If your password is correct, you will be presented with screen similar to the following.

ENTER CURRENT PASSWORD FOR COFFEE-                                           
COFFEE LOGON IN PROGRESS AT 12:32:31 ON MAY 5, 2020                          
NO BROADCAST MESSAGES                                                        
*                                                                           *
*                                                                           *
*                    Welcome to the TSO system on TK4-                      *
*                    =================================                      *
*                                                                           *
*                                                                           *

Hitting enter twice more will bring you to the TSO applications menu. You have now logged onto the system.


To logoff exit to a TSO READY prompt (pressing PF3 repeatedly). From the prompt type LOGOFF and hit enter.

Coming Soon

  • Types of dataset and how to use them
  • Using batch jobs with JCL
  • Navigating ISPF/RFE/RPF
  • Transferring Files