HP-UX SNAplus2 R7 Administration Guide

Introduction to SNAplus2
SNAplus2 Resources
Dependent LUs
Type 0–3 LUs are referred to as dependent LUs; they can support only one user session at a time, and a
session is controlled by the host program. Type 6.2 LUs can also be dependent LUs if they are used to
communicate with host computers running older versions of SNA host software.
LU types 0–3 are sometimes referred to as “old LUs,” and are used to communicate with hosts using 3270
emulation, RJE or LUA.
Type 0–3 LUs can also be grouped into LU pools, as described in Section 2.4.2,
Session Resources.In
addition, dependent type 6.2 LUs can be assigned to default pools, as described in Section 2.4.2, Session
Resources.
Independent LUs
LU type 6.2 is used to communicate with either hosts or peer computers using APPC or CPI-C.
Type 6.2 LUs that are used to communicate with peer computers, or with newer SNA software on host
computers, are referred to as independent LUs. Independent LUs can support multiple user sessions
simultaneously.
Dynamic Definition of Dependent LUs
Dynamic definition of dependent LUs (DDDLU) is a host feature that enables dependent LUs on the SNA system
to be added to the host configuration when the communication link from the SNA system to the host is established.
With DDDLU, LUs do not have to be configured statically at the host. (You must still define dependent LUs on
the SNAplus2 node.) This reduces the initial configuration required at the host, and makes later expansion easier.
SNAplus2 can communicate with both DDDLU-capable and non-DDDLU-capable hosts, with no difference in
the configuration required. When the communications link from the SNAplus2 node to the host is established,
a DDDLU-capable host informs the node that it supports DDDLU; the node then sends the required information
to define the dependent LUs that use the link. If the host is not DDDLU-capable, SNAplus2 does not send this
information; it assumes that the LUs have already been defined statically at the host.
LU Pools
Type 0–3 LUs can also be grouped into LU pools, so that a user session can be assigned to a pool of LUs. For
3270, RJE and LUA applications, you can use LU pools to simplify configuration and give greater flexibility.
All of the LUs in a pool must be the same type. For example, you can define several 3270 display LUs in a single
LU pool, then configure multiple 3270 display sessions using this LU pool. This makes configuring 3270 sessions
easier and enables any 3270 session to use any LU in the pool.
Note
You can assign a user’s session either to a specific LU or to an LU pool.
• If you assign the user’s session to a specific LU that is in a pool, the session uses this
LU if it is available; otherwise it uses any free LU from the pool, as though you had
assigned it to the LU pool instead of the specific LU.
• If you want the user to use only a specified LU, so that the user’s session cannot be
established if the LU is already in use, ensure that the LU is not in a pool.
LU pools can also span multiple SNAplus2 servers—just define LU pools with identical names on the different
servers. Clients that use the LU pool can then use any server. This means that the clients can still be used if a
server fails or is taken out of service. Using LU pools also simplifies client configuration and makes it easy to
increase capacity by adding another server or by adding LUs on an existing server.
LU pools support the following operations:
• Assigning LUs to users on a “first come, first served” basis when there are more users than LUs.
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