Introduction to CPSM Load management

CPSM (Cicsplex System Manager) is an IBM-provided tool for centralizing management of Cicsplex. The user uses CPSM, can carry on the Cicsplex level resource definition management, the system and the resources real-time monitoring, the topology management, the load management and so on. In this article, I will describe the load management features of CPSM, as well as the factors that affect the choice of AOR in the process of dynamically routing the load.

When a transaction that supports dynamic routing arrives in Tor, the CPSM load management module is tuned, CPSM performs arithmetic operations based on user preset load management rules, selects the most appropriate AOR in the AOR group defined by the rule, and routes the payload to the AOR for execution. CPSM provides a variety of algorithmic types, including queue algorithms (queues algorithm) and target algorithms (Goal algorithm), as well as lnqueue algorithms and lngoal algorithms that are added to the CICS TS 4.2 and later versions. These four algorithms are suitable for different user scenarios, among which the queue algorithm is the most applied.

As shown in the figure above, in the queue algorithm, a number of factors together determine the CPSM routing. It is roughly divided into two main parts: Load index and Health index (Health).

The load metric is used to mark the current load state of the AOR, and the factors to consider include:

1.MAXTASK's setting

2. Number of current tasks

Connection Agreement between 3.TOR and AOR

Health metrics are used to mark the current AOR for exceptions, and CPSM's algorithmic logic is usually to avoid sending transactions to unhealthy AOR. Among the factors to consider include:

1. System dump and transaction dump are present

2. Is there a memory shortage (SOS)

3. Whether the appearance of MXT

4. Whether the appearance of stall

5. Whether there is a connection interrupt

6. Whether the appearance of Abend

According to the above factors, CPSM will eventually calculate the routing value of each AOR and select the AOR with the lowest route value as the final target region. For affinity (Affinity) transactions, CPSM will be defined by the affinity rules to route the transaction to the specified CICS region to ensure the proper execution of the transaction.

The target algorithm (Goal algorithm) is based on the queue algorithm, considers the setting of z/Os WLM rule, and ensures that the transaction can meet the WLM rule setting in response time.

Lnqueue and Lngoal two algorithms, which are based on queue and goal, eliminate the role of connection protocol in algorithm operation. This means that regardless of whether Tor and AOR are on the same lpar, what connection protocol is used between Tor and AOR, and that the AOR connected to Tor will be treated equally in the calculation of route values.

If a user wants to implement dynamic routing of a transaction, it needs to be defined by Wui routing rules (Wlmspec), and the CPSM algorithm can be specified at Wlmspec definition.