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This chapter describes how to utilize zIIP processors with CA XCOM Data Transport to help reduce CPU utilization costs.
This section contains the following topics:
What features can run on zIIP?
zIIP is a special processor that is restricted to executing specific types of SRB mode work. It is intended to free up general computing capacity and lower the overall cost of computing for CPU intensive workloads.
CA XCOM Data Transport will attempt to offload data compression and de-compression functions to a zIIP when available. Given that data compression and de-compression accounts for a significant portion of CPU utilization for a data transfer, moving this processing to a zIIP will reduce utilization and costs.
Enabling CA XCOM Data Transport to enable zIIP support requires that the installation have CA Common Services for z/OS installed at the r11 release or higher. An APAR is required to be installed for both the r11 and r12 releases of CA Common Services for z/OS which introduces the zIIP Enablement Service. For the r11 release, APAR RO27636 must be installed. For the r12 release, RO27110 must be installed. The common services library must be available to the XCOM Server started task or XCOMJOB TYPE=EXECUTE job.
By default, CA XCOM Data Transport will enable zIIP support providing that the zIIP Enablement Service is available to load. There is a PARM and configuration parameter which can be specified to disable the zIIP support. The parameter is ZIIP=YES|NO, with YES being the default.
To insure that data compression and de-compression functions are eligible to be moved to the zIIP without impacting performance, CA XCOM Data Transport requires that the size of the data block being compressed or de-compressed is a minimum of 4096 (4 K) bytes. This is to insure that the overhead of switching the workload to the zIIP does not affect performance of the transfer.
We recommend that the configuration parameter MAXPACK is set to a minimum of 4096. The higher the value for these parameters, the more efficient the use of zIIP is.
For any transfer, PACK=LENGTH is specified to insure that the 4-K minimum size for compression on the zIIP is realized. Without this parameter, the record size of data in a file would need to be 4 K to move the compression or de-compression workload to zIIP.
CA XCOM Data Transport provides some facilities for managing and monitoring zIIP usage. The only goal of utilizing zIIP is to reduce CPU utilization and therefore the costs associated with that utilization.
A feature of zIIP Enablement Services provides an API to gather usage statistics for both normal and zIIP CPUs. For each transfer statistics about zIIP usage are written into the history record and SMF record. This data consists of six fields which can then be reported on through a TYPE=HISTORY job. Also supplied CA Easytrieve reports, or by way of the ISPF file transfer detail panel.
For transfers that do not utilize compression, statistics are still gathered. However the numbers for zIIP times are minimal as the process of gathering the zIIP statistics utilizes the zIIP processor. CPU statistics are applicable for these transfers.
A new modify command for the CA XCOM Data Transport Server is being provided to both report on status and allow zIIP support to be enabled/disabled.
The ZIIP,STATUS command will provide information about the CPUs (standard and zIIP) as to how many are defined and online. It will also display the status of zIIP support for the various features of CA XCOM Data Transport that can exploit use of zIIP. Currently this is only data compression and de-compression. Finally, statistics will be displayed which show the total amount of processing time that was eligible to run on zIIP and that actually executed on zIIP.
The STATUS command is also issued on startup and termination of the CA XCOM Data Transport Server and XCOMJOB TYPE=EXECUTE start and termination.
The ZIIP,ENABLE and ZIIP,DISABLE commands allow an administrator to either enable or disable the zIIP support for future data transfers. Any transfers currently in progress will continue to operate in the state that was active at the start of the transfer.
In the event of an abend that occurs while the transfer is running on a zIIP, CA XCOM Data Transport will handle the abend, disable future use of zIIP, and restart the transfer from the last checkpoint. On the restart, zIIP will not be used due to the disabling of the support.
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