| With heavy incoming connection/transaction workload with Connection Concentrator (CC) turned on the db2disp process can consume considerable amount of the CPU that can cause spikes up to 100% - depending on the load. We recommend customers add additional CPU to accommodate this load. This issue occurs rarely, but we would like to inform customer about this behavior.
In some environments the problem CPU spikes can be resolved by turning off the connection concentrator, but there are occasions when the Connection Concentrator is required for even workload distribution for SYSPLEX members on zOS db2 server.
For example:
When CC is OFF the workload distribution occurs on the connection boundaries and for long running connections there is no workload re-distribution during the life time of the connection.
When CC is ON, the re-distribution of work happens on transaction boundaries. When this happens, the server list cache on the gateway is updated (this is like connecting, so we get a fresh server list with new WLM weights).
In order to have the even workload distribution among the SYSPLEX members on zOS server the DB2 Connect server should have the following APARs installed:
IZ18588 v8 FP17: http://www-01.ibm.com/support/docview.wss?uid=swg1IZ18588
IZ18672 v9.1 FP6: http://www-01.ibm.com/support/docview.wss?uid=swg1IZ18672
IZ18766 v9.5 FP2: http://www-01.ibm.com/support/docview.wss?uid=swg1IZ18766 and Connection Concentrator turned ON.
There is other opportunity to reduce the workload on the DB2 Connect server and distribute this workload among the application servers by using the direct connection to zOS server. At the time of writing this technote only the jdbc driver can perform the Sysplex Workload Balancing and Connection Concentration.
The connection concentrator and sysplex work load balancing can be enabled by setting the following properties on the datasource or in a URL.
enableConnectionConcentrator=true
enableSysplexWLB=true
Here is the link
https://publib.boulder.ibm.com/infocenter/db2luw/v9r5/index.jsp
The sysplex feature was implemented in the driver that was shipped out with DB2 V8 FP10. But at that time the sysplex feature was only supported by datasource properties. The driver manager support of the sysplex feature was added in the driver that was shipped with DB2 V9.5.
Please keep this in mind:
If the sysplex (load balancing feature) is enabled in the driver and all the connections are going via DB2Connect to DB2 zOs then the driver will silently disable the load balancing feature in the driver. The reason is that in this case the driver expects the load balancing to be turned on in DB2 Connect.
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