Associating TPs and LUs with the Appropriate Level

The use of levels for TP profiles and LUs allows an installation to control access to its TPs. Because the use of levels involves searching, you can reduce processing overhead and DASD I/Os by associating the appropriate level of TP with the appropriate LU.

A single TP can have profiles for three levels:

System TP profile: One available for all users on the system (highest level)
Group TP profile: One for a specified group of users
User TP profile: One for an individual user (lowest level).

When APPC/MVS receives an incoming allocate request for a TP with more than one profile, it uses the TP profile with the lowest level to which the requestor has access.

Local LUs are also defined with a system, group, or user level to control the level of TP that runs in APPC/MVS.

System: An LU with a TP level of system allows only requests for system TP profiles. A request passing through this LU can access only system-level TP profiles.
Group: An LU with a TP level of group allows requests for group and system TP profiles. A request passing through this LU first attempts to access group-level TP profiles and then system-level TP profiles.
User: An LU with a TP level of user allows requests for user, group, and system TP profiles. A request passing through this LU first attempts to access user-level, then group-level, and finally system-level TP profiles.

The results of attempting to access a particular level of TP profile through an LU defined to a specific level are shown in Table 1. The search starts at the lowest level of access and stops as soon as a match is found.

Table 1. Local LU and TP profile level interactions
TP Level of LU	Profiles Searched	Profiles Not Searched
System	System TP profiles	Group and User TP profiles
Group	Group then System TP profiles	User TP profiles
User	User then Group then System TP profiles	None

To prevent unnecessary searching, assign system level TPs to system level LUs and avoid mixing system level TPs with user and group level TPs.