Before users can log on to TSO/E, you must make certain data sets available to the system. These data sets are needed to regulate access to the system and to store messages intended for terminal users. If RACF® is used for TSO security, the SYS1.UADS data set is optional, and the security access (UACC value) should be NONE.

• Regulating Access to the System
  To regulate access to the system, you can use either the RACF data base or SYS1.UADS, the user attribute data set (UADS).

  • If RACF is installed, you can use the RACF data base to regulate access to the system and store information about each TSO/E user. The RACF data base contains profiles for every entity (users, data sets or groups) defined to RACF. If you use the RACF data base to maintain information about TSO/E users, additional information about users is also stored in the RACF data base. For more information about the RACF data base, see .

    To add, change and delete user IDs, use RACF commands or panels. provides an overview of the RACF commands you can use to maintain user information.

  • If RACF is not installed, you must use the user attribute data set. The UADS is basically a list of terminal users who are authorized to use TSO/E.

    To add, change and delete user IDs, use the TSO/E ACCOUNT command. The ACCOUNT command and its subcommands are described in .

  To use the RACF database instead of the UADS to store information about each TSO/E user, convert user information that is defined in the UADS to the RACF database. You can convert all or only some user IDs to the RACF data base. TSO/E continues to retrieve user information from the UADS for user IDs that are not converted to the RACF data base. For more information, see Using the RACF data base to maintain TSO/E users.

  An advantage of using the RACF data base instead of the UADS is that maintenance of user ID information is simpler. You can use RACF commands to maintain TSO/E users and allow them to use the RACF security functions. Adding, changing, and deleting user ID information is simpler using the RACF data base because you use only RACF commands.

• Storing Messages Intended for Terminal Users

  The broadcast data set, for example, SYS1.BRODCAST, contains messages intended for terminal users. These messages are sent using the SEND command or the SEND subcommand of OPERATOR. The broadcast data set contains messages intended for all users (notices) and messages sent to individual users (mail). When you use either RACF commands or the ACCOUNT command and its subcommands to add, change or delete user information, the broadcast data set is updated simultaneously.

  As an alternative to using the broadcast data set to store messages sent to individual users (MAIL), you can store messages in a separate user log for each user. However, the broadcast data set is needed to store messages intended for all users (NOTICES). IBM® suggests implementing user logs to avoid the single point of failure that exists if all users rely on the broadcast data set for their individual mail.

  The broadcast data set is discussed in the sections that follow. For information about individual user logs, refer to Customizing how users send and retrieve messages.

• Maintaining the Required Data Sets

  If you decide to use the UADS and broadcast data sets to maintain TSO/E users, you must make both data sets available to allow users to log on. That is, if you are installing TSO/E on your system for the first time, you must create both data sets. If you are installing a new release of TSO/E, you may have to reformat both data sets. Periodically, you may have to reformat both data sets to eliminate wasted space caused by adding, changing and deleting information. See Working with the UADS and broadcast data set for more information.

  If you convert from the UADS to the RACF data base, you may have to reformat the broadcast data set periodically to eliminate wasted space caused by additions, changes and deletions. See Synchronizing the RACF data base with the broadcast data set for more information.

  You can change the number of records in the broadcast data set that are used for messages intended for all users (NOTICES). For more information, see Changing the amount of space reserved for notices.