Offloading the System Data Engine code to System z Integrated Information Processors

The System Data Engine can offload most of the code to run on System z® Integrated Information Processors (zIIPs). This operation frees the general-purpose processors (GCPs) for other work. It can also reduce software licensing costs.

About this task

Not all System Data Engine code is eligible to run on zIIPs. The System Data Engine must switch to task mode for the portion of code that must run in task mode, and switch back to Service Request Block (SRB) when that portion of code finishes running. The synchronization between task and enclave SRB creates additional overhead at the address space level. As a result, the total CPU time (GCPs plus zIIPs) when zIIP offloading is enabled is slightly higher than the total CPU time when zIIP offloading is not enabled. Therefore, if the zIIP capacity on the logical partition is insufficient, do not enable the zIIP offloading function.

Procedure

To activate the zIIP offloading function, specify ZIIPOFFLOAD=YES in the PARM parameter in the EXEC statement of the System Data Engine started task procedure or batch job JCL as shown in the following example.

//HBOSMFCL EXEC PGM=HBOPDE,REGION=0M,TIME=1440,
//         PARM='SHOWINPUT=NO,ZIIPOFFLOAD=YES'
//STEPLIB  DD   DISP=SHR,DSN=HBOvrm.LOAD
//HBOIN    DD   *
SET IBM_SDE_INTERVAL = '1 MINUTES';
SET IBM_UPDATE_TARGET = 'PORT 61001';
SET IBM_FILE_FORMAT = 'CSV';
SET IBM_RESOURCE = 'IFASMF.SYS01.PERF';
//         DD   PATH='/etc/cdpConfig/SYS01.sde',
//         PATHDISP=(KEEP),RECFM=V,LRECL=255,FILEDATA=RECORD
//         DD   *
COLLECT SMF FROM &IBM_RESOURCE
  EVERY &IBM_SDE_INTERVAL;
/*
//HBOOUT  DD SYSOUT=*
//HBODUMP DD SYSOUT=*

If ZIIPOFFLOAD=YES is specified but no zIIPs are online when the System Data Engine address space is started, no work is offloaded to zIIPs.

The Resource Measurement Facility (RMF) provides information on zIIP usage to help you identify when to add more zIIPs to the logical partition. Also, fields in SMF Type 30 records allow you to know how much time is spent on zIIPs, and how much time is spent on running zIIP eligible work on GCPs. A high CPU time consumed on GCPs by work that is eligible for a zIIP indicates high contention on the zIIP processors. In this case, you must add more zIIPs to the logical partition, or specify ZIIPOFFLOAD=NO to disable the zIIP offloading function of the System Data Engine.