The Base Package Controls One User, One User Group, And Many Application Services

When the system is initially installed, the following information is setup:

Application services are created for all secured transactions in the base package.
A user identified by the user id SYSUSER is created.
A user group identified by the user group code ALL_SERVICES is created. This user group is associated with all application services accessible from the Main and Admin menus. This user group is given access to all access modes for all application services (i.e., all actions on all transactions).
The user SYSUSER is linked to the ALL_SERVICES user group. This means that this user has access to all transactions and all actions.

When you receive an upgrade:

New application services are added for the new transactions introduced in the release.
Existing application services are updated with changes in their access modes (e.g., if a new action is added to a transaction, its application service is updated accordingly).
The ALL_SERVICES user group is updated so it can access the new / changed application services.

CAUTION:

Important! With the exception of Field Level Security information, you should never add, change or remove the above information. This information is owned by the base package. It is provided so that an "initial user" has access to the entire system and can setup user groups and users as per your organization's business requirements. In other words, do not provide your own users with access to the ALL_SERVICES user group. In addition, if you introduce new transactions, do not add them to this user group. Rather, link them to the user groups you setup to manage your organization's business requirements.