Cloud Data Manager

Performance considerations

Parallelism-related parameters in the Model9 management server

The model9-local.yml file residing in the $MODEL9_HOME/conf/ path contains all default parameters. The main section is ‘model9’ (lower-case letters), and all parameters should be indented under the model9 title as shown in the following example:

model9.parallelism.datasets.numberOfThreads: 10
model9.parallelism.volumes.numberOfThreads: 10
model9.parallelism.unix.numberOfThreads: 10
model9.parallelism.numOfFailuresPerAgent: 5

Parameter

Description

Default

model9.parallelism.dataset.numberOfThreads

Number of parallel threads running during dataset backup or archive

10

model9.parallelism.volumes.numberOfThreads

Number of parallel threads running during volume full dumps

10

model9.parallelism.unix.numberOfThreads

Number of parallel threads running during z/OS UNIX files backups

10

model9.parallelism.numOfFailuresPerAgent

Number of tolerated failures before removing an Agent from a policy run

5

Improving zIIP utilization

Simultaneous Multithreading (SMT)

Working in multi-threading (MT) mode allows you to run multiple threads per zIIP, where thread is comparable to the definition of a CP core in a pre-multi-threading environment, resulting in increased zIIP processing capacity. To enable zIIP MT mode, define the PROCVIEW parameter of the LOADxx member of SYS1.IPLPARM in order to utilize the SMT function of z/OS. It defines a processor view of the core, which supports from 1 to ‘n’ threads. Related parameters are MT_ZIIP_MODE and HIPERDISPATCH in IEAOPTxx. See z/OS MVS Initialization and Tuning Reference for more information.

WLM service class considerations

  • The agent utilizes zIIP engines. If the production workload also utilizes zIIP, associate the agent with a service class of a lower priority than the production workload service class, to avoid slowing down the production workload.

  • When issuing CLI commands in a highly-constrained CPU environment, verify that the issuer - whether it is a TSO userid or a batch job - has at least the same priority as the agent.

zIIP-eligible work running on CP

zIIP on CP reporting

Turning zIIP on CP monitoring provides information on zIIP-eligible work that was overflowed to CP. The monitoring is enabled by default only when zIIP processors are configured to the system. If no zIIP processors are configured and you would like to see how much CP would be saved by configuring zIIP processors in the system, you can set the PROJECTCPU‌ parameter to YES in IEAOPTxx. This would enable monitoring and cause the zIIP on CP chart to be displayed in the agent screen. See z/OS MVS Initialization and Tuning Reference for more information.

System wide settings

The system-wide settings of whether to allow spill of zIIP-eligible work to CP is defined in the IIPHONORPRIORITY parameter of IEAOPTxx. The default is YES, allowing standard CPs to execute zIIP and non-zIIP-eligible work in priority order. See z/OS MVS Initialization and Tuning Reference for more information.

Individual service class settings

The "honor priority" parameter allows limiting individual work from overflowing to CP regardless of the system-wide settings. Using the parameter may result in degradation in response time. See z/OS MVS Planning: Workload Management for more information.

Improving TCPIP CPU usage and throughput

Segmentation offloading

TCPIP supports offloading the work of segmentation to the OSA Express card. This feature reduces CPU usage and increases network throughput. It can be enabled via the IPCONFIG SEGMENTATIONOFFLOAD on the TCPIP profile.

MTU Maximum Transmission Unit size

Every TCPIP frame is broken down into the MTU defined by the system. The z/OS default MTU value of 512 is very small and introduces unnecessary TCPIP CPU overhead. The minimum value to be used as MTU when writing to object storage should be 1492.

Check with your network administrator whether jumbo frames can be utilized to further reduce the CPU overhead and improve throughput. Display the current MTU value using the commands:

Command

Description

TSO NETSTAT GATE

The “Pkt Sz” column represents the MTU size for each configured route. Verify the MTU size used by the route to the object storage. If no specific route to your object storage exists, the “Default” route value is used. This value should be equal or greater than 1492.

TSO PING <object-storage-ip> (PMTU YES LENGTH 1400

This command verifies whether the entire path from this TCPIP stack to the object storage supports at least 1400 sized frames. If the output of this command includes “Ping #1 needs fragmentation”, contact your network administrator in order to resolve this issue.