Introduction to SNAplus2

SNAplus2 Resources

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.

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.

•Balancing the traffic from user sessions across multiple servers or multiple host links, by defining a pool containing LUs on more than one node or on more than one host link.

•Permitting access to more than one host system from the same configuration, so that if one host system becomes unavailable, sessions can still be established to another system without requiring reconfiguration.

Chapter 2

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