IBM Session Manager Implementation

200 IBM Session Manager Implementation

IP entity advertising the distributed DVIPA and dispatching connections destined

for it is itself a system image within the sysplex, referred to as the distributing

stack.

Like Network Dispatcher and DNS/WLM, Sysplex Distributor also makes use of

Workload Manager (WLM) and its ability to gauge server load. In this paradigm,

WLM informs the distributing stacks of this server load so that the distributing

stack may make the most intelligent decision regarding where to send incoming

connection requests. Additionally, Sysplex Distributor has the ability to specify

certain policies within the Policy Agent so that it may use QoS information from

target stacks in addition to WLM server load. Further, these policies can specify

which target stacks are candidates for clients in particular subnetworks.

In certain scenarios, a round-robin distribution might be appropriate for specific

server applications. You can select round-robin distribution among DVIPA/port

targets for a particular application, rather than distribution based on capacity and

policy information, through a configuration option. This DISTMethod value does

not have any affect on incoming connection requests that have an active affinity

established to a specific server instance (through the TIMEDAFFINITY

parameter). When an affinity exists, it has priority over the DISTMethod setting.

As with Network Dispatcher, connection requests are directed to the distributed

stack of Sysplex Distributor. The stack selects which target server is the best

candidate to receive an individual request and routes the request to it. It

maintains state so that it can forward data packets associated with this

connection to the correct stack. Additionally, data sent from servers within the

sysplex need not travel through the distributing stack.

Sysplex Distributor also allows a DVIPA to move nondisruptively to another

stack. In the past a DVIPA was only allowed to be active on one single stack in

the sysplex. This led to potential disruptions in service when connections existed

on one stack, yet the intent was to move the DVIPA to another stack. With

Sysplex Distributor, the movement of DVIPAs can now occur without disrupting

existing connections on the original DVIPA owning stack.

7.3.2 Our Dynamic DVIPA configuration

The following command may be issued to view the DVIPA configuration.

Example 7-1 VIPADYNAMIC

D TCPIP,TCPIPA,SYSPLEX,VIPAD

EZZ8260I SYSPLEX CS V1R5 717

VIPA DYNAMIC DISPLAY FROM TCPIPA AT SC48

IPADDR: 10.1.6.150 LINKNAME: VIPL0A010696

ORIGIN: VIPADEFINE