Saving Software Costs with Group Capacity Richard S. Ralston OHVCMGMay 13, 2010

Abstract/Topics  What are Group Capacity Limits?  Benefits of Group Capacity Limits  How to define a group and its limit  Determining where to set the group limit  When are group limits in effect?  Real-time Monitoring of Group Capacity Limits  Impacts of running under the group limit  Financial benefits of using group limits

What are Group Capacity Limits?  A Group Capacity Limit is similar to LPAR Defined Capacity except it defines the Software MSU Limit for a group of LPARs. Identifies the billing point for the group. When the 4 hour rolling average exceeds the Group Capacity Limit, CPU resource is limited to the Group Capacity Limit  The grouped LPARs must all be on the same CEC.  They (the LPARs) may span sysplexes.  z/OS 1.8 or higher  z9 or z10

Benefits of Group Capacity Limits  Better control of your VWLC software cost  Better sharing of CPU resource amongst LPARs LPAR with greater need can use CPU resources that a LPAR Defined Capacity would prevent. LPAR(s) not using CPU resource ‘gives it up’ for the LPAR(s) needing them.  May choose to eliminate LPAR Defined Capacities and have fewer control points to tweak.

How to Define a Group and Its Limit  Done at the HMC.  SC System z9 Support Element Operations Guide Defining a group, page 6-40 Changing Group Capacity Limit, page 9-4  SC System z10 Enterprise Class Support Element Operations Guide Defining a group, page 6-41 Changing Group Capacity Limit, page 9-4

Determining Where to Set the Group Capacity Limit  Fast answer 1 - sum of your LPAR Defined Capacities Turn off LPAR Defined Capacities  Fast answer 2 – 3% Below your current SCRT MSU billing amount (sum of the LPAR Defined Capacities) May turn off LPAR Defined Capacities Up to 10% may be easily acceptable/achievable when starting  Monitor your system usage and the 4 hour rolling averages and use some finesse to determine the Group Capacity Limit.  When adding a zIIP or zAAP you can reduce the Group Capacity Limit by the amount of CPU resource you will move to the zIIP or zAAP.  The same rules about when to set LPAR Defined Capacity apply to Group Capacity Limits.

Monitor & Finesse Propose reducing the Group Capacity Limit from 1475 to 1450.

Monitor & Finesse - Results This reduction of 25 Software MSUs had little impact on the duration of time running under the Group Capacity Limit.

Determining Where to Set the Group Capacity Limit – Exercise 1  Moving test CICS, DB2, IDMS and associated batch from an LPAR on LDC1 to a new LPAR on LDC2  The LPAR will be SW MSUs  Need to add 3 CPs to the machine  Need to determine the new Group Level Capacity

Determining Where to Set the Group Capacity Limit – Exercise 2 What size machine do I need with the new Workload?

Determining Where to Set the Group Capacity Limit – Exercise 3 Where do I set the Group Capacity Limit?

When Are Group Limits in Effect?  When the sum of the 4 hour rolling averages for the LPARs in the group is greater than the Group Capacity Limit.  All the LPARs in the group show that they are running under the ‘cap’ at the same time. Capping percentage for all LPARS > 0  On a z10 with hiperdispatch I have observed some periods (minutes) with one or more LPARs not capped and yet the overall group is capped.

Reporting  The RMF Postprocessor Group Capacity report reports after the fact.  SAS along with MXG or MICS  z/OS TDS  Other home grown reporting  The IBM Sub-Capacity Planning Tool and your favorite spreadsheet software

Group Capacity Limit Reached 1

Group Capacity Limit Reached 2

Capping Percentage 1

Real-time Monitoring of Group Capacity Limits  There are no good tools that I am aware of.  Need to sum the 4 hour rolling averages for each LPAR in the group and compare the sum against the Group Capacity Limit.  Best I’ve found so far: RMF PM Display the %WLM Capping for each LPAR Display the 4 Hour Rolling Average for each LPAR  2 nd Best – Customized View in RMF Data Portal Free RMF/Browser tool – built into RMF Monitor III IP Address:  nnn.nnn.nnn.nnn is the IP address of LPAR running GPMSERVE ftp://ftp.software.ibm.com/eserver/zseries/zos/rmf/RMF_MonitorIII_ DataPortal.pdf ftp://ftp.software.ibm.com/eserver/zseries/zos/rmf/RMF_MonitorIII_ DataPortal.pdf  The Group Capacity Limit is not a displayable field with these tools.

Sample RMF PM Display

Impacts of Running Under the Group Capacity Limit  LPAR Weighting Factors are Important! Weighting Factors not only determine LPAR dispatching priority, but the percentage of the machine the LPAR gets when under the Group Capacity Limit. Important work in a small LPAR may need a higher Weighting Factor than the algorithm(s) indicate.  WLM Class definitions and Policy are Important! Lower priority work may suffer if the Group Capacity Limit is too low.  If an LPAR is scrunched too far by Group Capacity Limits Batch (lower priority work) will take longer Online response time may suffer

Financial Benefits of Using Group Capacity Limits  You can lower your VWLC software cost by using Group Capacity Limits.  Determine your incremental software cost, $/MSU Need 2 consecutive months bill $/MSU = (m2$-m1$) / (m2msu-m1msu)  Savings = $/MSU * MSU Reduction  Example: Savings = $300 * 25 = $7500/month  Your results will vary.

What’s Next?  Automatically changing Group Level Capacity through the HMC API. Lower Group Level for non-Prime hours. Prevent SW bill from being set during non-Prime time.  Article for zJournal

Thanks  Kelly Vogt - Humana  Al Sherkow - I/S Management Strategies, LTD.  Myron Highfield - IBM

Questions/Discussion Thank You!

Contact Info Richard Ralston