Introduction

Time Sharing Option is the main "command line" utility that you will be using on the mainframe system.

It allows users to share the system and gain shared access to z/OS resources
Each user will need to identify themselves to TSO using a terminal, with their login and password

Tasks or commands submitted by the users will share the CPU time, meaning some tasks might have to wait their turn.

Without TSO, or a similar product you wouldn't be able to do things in real-time, for example it would be impossible to edit a dataset in real time, as all of those operations would need to be performed in a batch transaction.

TSO is essential, you can manipulate all source data sets, compile and link programs interactively, view the compiled output or send it to a printer, as well as simply test your programs before incorporating them into batch processing scripts.

You can also dynamically allocate, list , copy, delete, rename or retrieve information about data sets without the need for complex JCL

When logging in via VTAM you might need to specify that you want to use TSO, which you can specify with TSO

After entering the password, you might need to press enter a few times to get past messages that show up initially, eventually you will be dropped at the READY prompt, and you can start issuing commands or go into another product like ISPF

If the screen you're on has three asterisks at the bottom left (***) that means that there is more text coming, but it all couldn't fit on the screen and you might need to press enter to display more of it.

Data set naming convention

For most users their user ID will become a prefix for all data sets created by the TSO session.
For example if your username is IBMUSER then by default the data sets you create will start with it. For example IBMUSER.TEST.FILE
The naming convention goes

PROJECT.GROUP.TYPE

There are many standards often user, but remember that each segment can have a maximum of 8 characters, starting with a letter or the @,#,$ characters.
The entire length of the data set name (including the dots) must also not exceed 44 characters.

TSO Commands

There are many commands you can issue in TSO, with some examples shown below:

LISTCAT will allow you to search through catalogs and list entries within them.
LISTDS will allow you to list data set information
RENAME will allow you to rename non-VSAM data sets and create aliases for member data sets
LOGOFF will simply terminate the current TSO / ISPF session
LOGON will achieve the same thing as LOGOFF, but will also drop you directly into a login prompt.
ALLOCATE will allow you to allocate new data sets on the systems
FREE will allow you to free a data set (remove it)
LISTALC will allow you to see data sets currently assigned to you
XMIT will allow you to transmit a data set in situations where CPUs are not connected through DASD
RECEIVE will allow you to receive the data set being sent with XMIT