Working with the UADS and broadcast data set

If you are installing TSO/E on your system for the first time, you must create both the UADS and the broadcast data sets. If you are installing a new release of TSO/E, you may have to reformat both data sets. During subsequent operation, you may have to update both data sets by adding, changing, or deleting entries. In addition, you may reformat the data sets to eliminate wasted space caused by periodic additions, changes, and deletions.

When allocating or processing the UADS and the broadcast data set, take the following into account:

Do not allocate either SYS1.UADS or the broadcast data set on shared DASD that is accessed by more than one processor, unless you use global resource serialization. See Global resource serialization for additional information.
If SYS1.UADS is modified by programs other than the reformatting program (UADSREFM) or the ACCOUNT command, unpredictable results may occur later during reformatting, or during processing using the subcommands of ACCOUNT.
Do not move or copy either data set. If you want to allocate them to different volumes, or change their attributes or sizes, read Reformatting the UADS and the broadcast data set and Changing the allocation of the broadcast data set.
With RACF® installed, your installation can use security labels. If security labels are being used at your installation:
- SYS1.UADS should be defined to RACF with a UACC(NONE) and SECLABEL(SYSLOW), and
- The broadcast data set should be defined to RACF with a UACC(READ) and SECLABEL(SYSLOW).
  Users that have ACCOUNT authority must be given UPDATE authority to the UADS and broadcast data set.
  
  If the RACF SECLABEL class is active and the RACF SETROPTS MLS option is in effect, the user of the ACCOUNT command must log on using the SYSLOW security label to use the ACCOUNT command. For information about the SECLABEL class, the SYSLOW security label, and SETROPTS options, see z/OS Security Server RACF Security Administrator's Guide.

When allocating the UADS, reserve enough space to accommodate all of the users you plan to allow to use TSO/E. Each user requires an entry in the directory and a member in the data portion. Choose a block size for the data portion that makes the most efficient use of storage. The block size should be large enough to contain all of the logon data for most users. To determine if the block size for an existing UADS is large enough list the data set's members. If several users have more than one entry, you should increase the block size. Note that one block is used for each user record.

When creating or enlarging the broadcast data set, reserve enough space to ensure that the data set does not become full. If the data set does become full, additional messages cannot be stored. In addition, reallocating the data set causes the contents to be lost.

When creating a new UADS or broadcast data set on the same volume as the old data set, TSO/E can use the new data sets without an IPL, however, we suggest that you IPL your system. If you are creating a new UADS or broadcast data set on a different volume, you must IPL your system.