Sysplex distributor policy performance monitoring configuration
Before activating the sysplex distributor policy performance monitoring function, see Policy interactions for information on workload balancing and policy interactions with sysplex distributor.
The following example illustrates how to activate the policy performance
monitoring function for sysplex distributor.
Note: This
function is activated on SD target servers and is used to
monitor the performance of outbound traffic being serviced by the
target servers. The goal is to detect TCP traffic that exceeds
defined thresholds for dropped packets or time-outs, and derive a
default QoS weight fraction for the target server. This default
QoS weight fraction is then used to reduce the WLM weight assigned
to the target servers, so that the SD distributing stack
can take QoS performance into account.
The following statements apply to the example in this topic:
- The policy performance monitoring sampling interval is 60 seconds.
- Policy Agent assigns a loss ratio weight fraction of 25% when the TCP loss ratio (dropped packets to total packets) starts to exceed 2%.
- The loss ratio weight fraction is increased to 50% when the loss ratio starts to exceed 4%, continuing in this manner up to the maximum loss ratio weight fraction of 95%.
- In a similar manner, a TCP timeout weight fraction of 50% is assigned when the timeout ratio starts to exceed 5%, increasing up to a maximum timeout weight fraction of 100%.
- The loss ratio weight fraction and TCP timeout weight fraction are added together to form a single default QoS weight fraction for the target server, up to a maximum of 100%. When the Traffic Regulation policy connection limit reaches constrained threshold (90%), the default QoS weight fraction is set to 100% and forces SD to route requests to other target nodes with better routing weights.
- The default QoS weight fraction is used at the SD distributing stack to reduce the WLM weight. For example, if the WLM weight is 40, a weight fraction of 50% results in the weight being reduced to 20.
- The traffic to be monitored must be represented by at least one Differentiated Services policy defined for the target application (in this example a policy is defined for Telnet).
- An additional Policy Action weight fraction is calculated
for a target's DVIPA/Port if there are any active connections to the
target using that service level.
The Policy Action weight fraction is calculated as the largest of three fractions:
- The number of active connections to this target DVIPA/Port will
be compared with the maximum connections allowed for this Policy action.
- When the number of active connections reaches 50% of maximum connections, then the Policy Action weight fraction will be set to MAX (50%, current calculated value).
- When the number of active connections reaches 65% of maximum connections, then the Policy Action weight fraction will be set to MAX (85%, current calculated value).
- When the number of active connections reaches 80% of maximum connections, then the Policy Action weight fraction will be set to 100%.
- The throughput rate for this timer interval will be calculated and compared to the DiffServ mean rate of this Policy action. If the throughput rate is greater than 85% of the DiffServ mean rate, the average throughput rate per connection will be calculated. If the throughput rate per connection is less than the DiffServ min rate, the minimum throughput requirement per connection is not being met and the Policy Action weight fraction will be set to 100%.
- The default QoS weight fraction.
- The number of active connections to this target DVIPA/Port will
be compared with the maximum connections allowed for this Policy action.
- Only one policy rule and policy action are defined here.
As a result, only Telnet QoS performance information is monitored by the Policy Agent for sysplex distributor to route incoming Telnet connections to this target node relative to other target nodes which presumably can also accept Telnet requests.
PolicyPerfMonitorForSDR enable { samplinginterval 60 LossRatioAndWeightFr 20 25 TimeoutRatioAndWeightFr 50 50 LossMaxWeightFr 95 TimeoutMaxWeightFr 100 MaxConnWeightFr 50 65 80 }policyAction telnetGold { MinRate 500 # Provide minimum rate of 500 Kbps. OutgoingTOS 10100000 # the TOS value of outgoing telnet packets. } policyRule targetelnet { ProtocolNumberRange 6 SourcePortRange 23 policyactionreference telnetGold }