DS8000 HyperPAV UCB/Aliases Analysis Case Study for ... - IBM

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DS8000 HyperPAV UCB/Aliases Analysis Case Study for ACME Brokerage Firm JoAnne Brown, Accredited IT Specialist, IBM – Advance Technical Support © Copyright 2007, IBM Corporation Version 1.0 - 1 - http://www.ibm.com/support/techdocs DS8000 HyperPAV UCB/Aliases Analysis Case Study for ACME Brokerage Firm

DS8000 HyperPAV UCB/Aliases Analysis

Case Study for ACME Brokerage Firm

JoAnne Brown, Accredited IT Specialist, IBM – Advance Technical Support

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DS8000 HyperPAV UCB/Aliases Analysis Case Study for ACME Brokerage

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Table of Contents

ABSTRACT ................................................................................................................................- 3 -

DISCLAIMERS..........................................................................................................................- 3 -

BACKGROUND.........................................................................................................................- 4 -

BENEFITS OF HYPERPAV.....................................................................................................- 5 -

HYPERPAV REQUIREMENTS ..............................................................................................- 5 -

HARDWARE.............................................................................................................................. - 5 -

SOFTWARE ............................................................................................................................... - 5 -

HYPERPAV – Z/OS OPTIONS AND COMMANDS.............................................................- 5 -

HYPERPAV MIGRATION ......................................................................................................- 6 -

HYPERPAV UCB/ALIASES ANALYSIS CASE STUDY .....................................................- 7 -

PROBLEM STATEMENT........................................................................................................- 7 -

ANALYSIS METHODOLOGY................................................................................................- 7 -

DATA COLLECTION .................................................................................................................. - 7 -

ANALYSIS OUTPUT................................................................................................................... - 7 -

ANALYSIS SAMPLE................................................................................................................... - 8 -

CURRENT ENVIRONMENT ..................................................................................................- 8 -

ANALYSIS RESULTS.................................................................................................................. - 8 -

PERFORMANCE – ALL DISK I/O................................................................................................ - 8 -

PEAK PERIOD ........................................................................................................................... - 9 -

UCB’S AND ALIASES IN USE BY LCU ..............................................................................- 10 -

HYPERPAV REQUIREMENT SUMMARY ........................................................................- 13 -

RESULTS AFTER HYPERPAV IMPLEMENTATION .....................................................- 13 -

RMF REPORTS.......................................................................................................................- 14 -

SUMMARY...............................................................................................................................- 14 -

ADDITIONAL READING AND REFERENCE MATERIAL ............................................- 15 -

Z/OS SUPPORT OF THE IBM TOTALSTORAGE ENTERPRISE STORAGE SERVER........................ - 15 -

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Abstract

This paper will present a case study for a HyperPAV UCB/Aliases analysis for IBM

DS8000’s. The case study will comprise of a justification for why do an analysis,

instructions on how to request the analysis, data gathering, and sample reports.

Disclaimers

IBM customers are responsible for ensuring their own compliance with legal

requirements. It is the customer's sole responsibility to obtain advice of competent legal

counsel as to the identification and interpretation of any relevant laws and regulatory

requirements that may affect the customer's business and any actions the customer may

need to take to comply with such laws.

IBM does not provide legal advice or represent or warrant that its services or products will

ensure that the customer is in compliance with any law.

The information contained in this documentation is provided for informational purposes

only. While efforts were made to verify the completeness and accuracy of the information

provided, it is provided “as is” without warranty of any kind, express or implied. IBM shall

not be responsible for any damages arising out of the use of, or otherwise related to, this

documentation or any other documentation. Nothing contained in this documentation is

intended to, nor shall have the effect of, creating any warranties or representations from

IBM (or its suppliers or licensors), or altering the terms and conditions of the applicable

license agreement governing the use of IBM software.

Acknowledgments

Thank you to the following reviews

Dave Heggen, Certified Consulting IT Specialist

Alison Pate, Certified Consulting IT Specialist

Brian Smith, IT Specialist

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Background

On October 30, 2006 IBM announced a new feature HyperPAV for all new and existing

DS8000 machines. HyperPAV is an IBM-only feature which provides exclusive benefits

in zSeries environments. With HyperPAV aliases are drawn from a pool from each

Logical Control Unit (LCU) and returned to the pool when the I/O is complete.

Within a z/OS system each z/OS device number has a dedicated Unit Control Block

(UCB) which holds information about an IO device, such as features of the device and

state information. An alias is a control block used to keep the status of a z/OS

input/output operation during pending, connect and disconnect time. In addition, the

installation can set aside some number of aliases for all of the devices associated with

each LCU.

Parallel Access Volumes (PAV) allows multiple concurrent I/Os to the same volume at

the same time from applications running on the same z/OS system image. This allows

applications to share the same logical volumes while improving performance. When an

I/O request is made to a base address z/OS uses the base UCB or one of its alias UCBs,

depending on its availability to the initiate the request. IO’s can be assigned to an Alias

by IOS once IOS bind the alias address to the base UCB. The benefit is a reduction in

IO device addresses, a reduction in IOSQ, and potential increase in throughput.

If the UCB is in use by an application what happens next depends on how the device is

configured.

• Before Parallel Access Volume (PAV) support, the request was “queued by IOS”.

The application waits until the operation in process and queued requests from

higher priority applications are finished. This process can elongate response

times for IO and in general slow down application performance. This is

• If the aliases are managed statically, some number of aliases is assigned to the

base when it is configured. This assignment remains the same until changed

manually. Alias devices are only used when the base device is busy

• With Dynamic alias management, aliases are managed initially as though they

were static, assigned to specific base volumes. Workload Manager (WLM)

manages aliases dynamically to achieve workload goals. Aliases will be

unbound from their present assigned base and assigned to another device within

the same Logical Storage Unit (LCU) based on measurement device activity and

the progress of applications using the devices involved.

• HyperPAV is an enhancement of the algorithms where aliases are not assigned

to any specific device number. When a LCU is initialized in HyperPAV mode,

aliases are placed in a pool available for all base address in the LCU and any

base device within the LCU will use an alias from the pool for the length of an I/O

operation if the UCB assigned to it is busy. If ALL aliases assigned to an LCU

are being used, the request will be queued.

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Benefits of HyperPAV

HyperPAV is intended to achieve equal or better performance than the original PAV

feature using the same or fewer z/OS resources. It gives you the benefits of dynamically

managed aliases, without intervention of WLM.

HyperPAV allows you to define aliases which are applicable to more devices (since they

are not statically used). The total number of aliases needed in an LCU equals the

maximum number of aliases needed by an attached LPAR. Actual mechanism for

ALIAS/BASE association is IBM Proprietary and was added to the 2107 attachment

specifications. In most cases the number of UCBs and aliases can be reduced

significantly. The reduction in aliases addresses will benefit zSeries customers who are

approaching the base addressing limit.

Using HyperPAV z/OS can react instantaneously to I/O load demands such as market

open conditions.

HyperPAV Requirements

Hardware

• DS8000 Bundle Version 6.2.4 or higher

• DS8000 FCP/FICON Host Adapters

• Licensed Features

o FICON/ESCON Attached (Turbo)

o PAV

o HyperPAV

Software

All PTFs needed for DS8000 support are documented in the Preventative Service

Planning (PSP) Bucket using the title 2107DEVICE.

http://www14.software.ibm.com/webapp/set2/psp/srchBroker

• IOS Support (if not present will require an IPL to install)

HyperPAV – z/OS Options and Commands

SYS1.PARMLIB(IECIOSxx)

HYPERPAV=YES|NO|BASEONLY

o YES – Attempt to initialize LCUs in HyperPAV mode

o NO – Do not attempt to initialize LCUs in HyperPAV mode

o BASEONLY – Attempt to initialize LCUs in HyperPAV mode, but only

start I/Os in base volumes.

Enhanced Commands

o SETIOS HYPEPAV=YES|NO|BASEONLY

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HyperPAV Migration

The HyperPAV feature can be enabled dynamically. It can take some time to initialize all

attached DS8000 LCUs into HyperPAV mode and some planning is recommended. If

many DS8000 LCU are involved choose a quiet time to perform the SETIOS

HYPERPAV=YES command. Do not schedule concurrent DS8000 microcode changes

or IODF activation to occur concurrently with this change.

No changes to the HCD or DS8000 logical configuration are required on existing LCUs, if

you are already using PAV and FICON.

The HyperPAV deployment should be staged after the hardware and software

requirements are fulfilled. The following steps are required for implementation:

1. Authorize and Load the HyperPAV feature on the DS8000

2. To run without exploiting the HyperPAV feature use the z/OS PARMLIB option

IECIOSxx

3. Enable the HyperPAV feature on z/OS images that you want to utilize the

HyperPAV using the PARMLIB or SETIOS command

4. Eventually enable the HyperPAV feature on all z/OS images in the Sysplex and

authorize licensed function on all attached DS8000s.

5. Reduce the number of aliases defined. See case study recommendations to

determine the correct number of aliases for your environment

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HyperPAV UCB/Aliases Analysis CASE STUDY

Problem Statement

The ACME Brokerage Firm is currently experiencing slow response time during market

open and close. Good response time during market open and close it vital to meeting the

service objectives at ACME.

ACME currently has two ESSs. They recently acquired a DS8000 and would like to take

advantage of the new HyperPAV feature when they migrate to the new DS8000.

The Field Technical Storage Specialist (FTSS) for ACME submitted a requested through

TechExpress via the following URL

http://dalnotes1.dfw.ibm.com/atss/techxpress.nsf/request?OpenForm for a HyperPAV

Study to determine their UCB and Alias usage.

After receiving the request a data collection guide was sent to ACME Brokerage Firm

along with instructions for FTPing data to Testcase.

The results are documented in the Analysis Results section.

Analysis Methodology

This analysis is based on the current use/activity of disk base/alias address as measured

by RMF. It examines the disk operations in process over a large number of samples and

assumes the future workload will look like the current workload. ATS offers a free

service to perform this analysis.

Data Collection

The RMF data needed is typically gathered continuously by zOS installations. The

analysis requires SMF records type 70 – 78. It is essential that RMF data accurately

represents the installation’s typical or peak workload. Whether you select a peak interval

or typical interval, is dependent on customer requirements. The customer should expect

a note within 24 hours after receiving the data describing the status of the data confirming

the data has been received and is suitable for processing.

Analysis Output

The analysis determines active UCB and alias request by LCU for each interval. The

report provides a comparison of the required number of UCBs and aliases for this

installation to the

128,000 UCB/aliases allowed in a zOS system.

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Analysis Sample

Current Environment

IBM – 12345

• LCU 0000 – 000F

IBM – 56789

• LCU 2000 – 200F

Analyzed RMF data from 6/11/2007 – 6/17/2007

Currently using Dynamic PAVs with 256 UCBs and Aliases allocated per LPAR

Analysis Results

Performance – All Disk I/O

This chart shows a summary of all the disk activity in the data received. The I/O rate is

shown as a purple line. The response time is showed as a stacked bar chart broken

down into the response time components. IOSQ (red) is the most important

measurement for the purpose of this study. IOSQ is the time for each I/O operation that

applications wait because there are not enough aliases to initiate a request. Customers

will see a performance improvement from HyperPAV if there is a significant amount of

red (IOSQ) in this chart. In this case the IOSQ time is between 17% - 25% of the

response time which is quite significant compared to other customers

The PEND (yellow) is the time per I/O operation waiting for the start of the subchannel

(SSCH). The CONN (green) is the time data is actually received. The DISC (blue) is the

time the device is logically disconnected from the subchannel.

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RT/ms

8

7

6

5

4

3

2

1

0

5:59 AM 11-Jun

6:29 AM

Peak Period

Average of IOSQ Average of PEND Average of CONN Average of DISC Average of I/O Rate

6:59 AM

5:59 AM 12-Jun

6:29 AM

6:59 AM

5:59 AM 13-Jun

6:29 AM

6:59 AM

5:59 AM 14-Jun

6:29 AM

Date & Time

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6:59 AM

5:59 AM 15-Jun

6:29 AM

Performance All Disk I/O 1

6:59 AM

5:59 AM 16-Jun

6:29 AM

6:59 AM

5:59 AM 17-Jun

The peak I/O rate for all control units was observed in the measurement interval which

started 8:14 am on 6/11/2007 and ended 8:29 am. During that period, an average of

82431 I/O operations was executed each second.

An average of 0.41 milliseconds was spent waiting in the IOS queue before acquiring a

UCB or an alias during the I/O operation. The UCB or an alias is then held 4.79

milliseconds during pend, connect, and disconnect time.

If you hold a UCB 4.79 for milliseconds 8243 times a second, you hold the UCB for

39483.97/1000= 39.48 seconds each second. From this analysis we can determine that

this workload consumes an average of 40 UCBs and aliases across all LCU, during the

interval.

6:29 AM

6:59 AM

8000

7000

6000

5000

4000

3000

2000

1000

0

IO Rate

UCB’s and Aliases in Use by LCU

This following chart shows the average number of UCBs + Aliases in use for each LCU

on IBM - 12345 from 6/11/2007 to 6/17/2007. On average there are 14 or less UCB +

Aliases in use during any 15 minute interval. Please note the spikes in UCB and Aliases

usage which occurs daily at 8am and 5 pm.

UCBs + Aliases in Use

16

14

12

10

8

6

4

2

0

6:14 PM

12:14 PM

6:14 AM

12:14 AM 11-Jun

Average of 0000' Average of 0001' Average of 0002' Average of 0003'

Average of 0004' Average of 0005' Average of 0006' Average of 0007'

Average of 0008' Average of 0009' Average of 000A' Average of 000B'

Average of 000C' Average of 000D' Average of 000E' Average of 000F'

6:14 PM

12:14 PM

6:14 AM

12:14 AM 13-Jun

6:14 PM

12:14 PM

6:14 AM

12:14 AM 12-Jun

6:14 PM

12:14 PM

6:14 AM

12:14 AM 14-Jun

Date & Time

6:14 PM

12:14 PM

6:14 AM

12:14 AM 17-Jun

6:14 PM

12:14 PM

6:14 AM

12:14 AM 16-Jun

6:14 PM

12:14 PM

6:14 AM

12:14 AM 15-Jun

UCB + Aliases in Use for DSS IBM-12345 2

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This chart shows the UCB and Aliases Usage for each LCU on IBM - 56789 on starting

on 6/11/2007 to 6/17/2007. On average there are 2 or less UCBs and Aliases in use

except for the spike which occurred on 6/16/2007.

UCBs + Aliases in Use

16

14

12

10

8

6

4

2

0

Average of 2000' Average of 2001' Average of 2002' Average of 2003'

Average of 2004' Average of 2005' Average of 2006' Average of 2007'

Average of 2008' Average of 2009' Average of 200A' Average of 200B'

Average of 200C' Average of 200D' Average of 200E' Average of 200F'

6:14 PM

12:14 PM

6:14 AM

12:14 AM 13-Jun

6:14 PM

12:14 PM

6:14 AM

12:14 AM 12-Jun

6:14 PM

12:14 PM

6:14 AM

12:14 AM 11-Jun

6:14 PM

12:14 PM

6:14 AM

12:14 AM 14-Jun

Date & Time

6:14 PM

12:14 PM

6:14 AM

12:14 AM 17-Jun

6:14 PM

12:14 PM

6:14 AM

12:14 AM 16-Jun

6:14 PM

12:14 PM

6:14 AM

12:14 AM 15-Jun

UCBs + Aliases in Use for DSS IBM-56789 3

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Here is the distribution of the number of UCBs and aliases in use on each LCU in each

measurement period. The leftmost bar says that somewhere between 0 and 0.5 UCBs

and Aliases were in use by all 15800 LCU samples. The next bar indicates that between

.5 and 1 UCBs and Aliases were in use by all of the LCUs in 3700 samples. This

represents 75% of the samples.

If you follow the 90% line for cumulative percent on the left of the chart, you will find that

90 percent of the time 1 or less UCBs and aliases were being used by a LCU

Samples

18000

16000

14000

12000

10000

8000

6000

4000

2000

0

SAMPLES

CUM%

0

0.5

1

1.5

2

2.5

3

3.5

4

4.5

5

5.5

6

6.5

7

7.5

8

8.5

9

9.5

10

UCBs & Alises in Use (PAVs)

Distribution of UCBs + Aliases 4

10.5

11

11.5

12

12.5

13

13.5

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100

90

80

70

60

50

40

30

20

10

0

Cum%

ACME Brokerage Firm is currently using Dynamic PAV technology. Even if they were to

increase the number of UCBs and Aliases to accommodate market open and market

close demands, it would not eliminate the IOSQ (red) time because WLM cannot react

instantaneously to the I/O demand. Dynamic PAV requires Workload Manager (WLM)

which only makes one change every 10 seconds.

HyperPAV requirement summary

The IOSQ time represents 23 percent of the response time in the morning and 17 percent

of response time in the evening. HyperPAV has the potential to eliminate or reduce the

IOSQ time and therefore reduce the response time.

ACME’s peak occurred on June 11, 2007 at 8:14 am to 8:29 am and during that time

there were 40 UCBs and Aliases in use on all LCUs.

Hyper-PAV requirement

Recommendations are per LCU and based upon the average usage with current

workloads

14 + 6 (margin) = 20 UCBs + Aliases per LCU

IBM – 12345

IBM – 56789

Results after HyperPAV Implementation

After implementing HyperPAV Acme Brokerage Firm response time during market open

and closed has been reduced by 17% - 25%.

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RMF Reports

The following RMF Monitor I Reports are available to monitor the PAV usage.

RMF I/O Queuing Activity Report

AVG AVG DELAY AVG

AVG DATA

LCU CU DCM GROUP CHAN CHPID % DP % CU CUB CMR CONTENTION Q CSS HPAV

OPEN XFER

MIN MAX DEF PATHS TAKEN BUSY BUSY DLY DLY RATE LNGTH DLY WAIT MAX

EXCH CONC

0 0000 C011 00 0.000 0.00 0.00 0.0 0.0

01 0.000 0.00 0.00 0.0 0.0

02 0.000 0.00 0.00 0.0 0.0

03 0.000 0.00 0.00 0.0 0.0

A1 0.000 0.00 0.00 0.0 0.0

B2 0.000 0.00 0.00 0.0 0.0

C3 0.000 0.00 0.00 0.0 0.0

D4 0.002 0.00 0.00 0.0 0.1

* 0.002 0.00 0.00 0.0 0.1 0.000 0.00 0.1 0.000 5

RMF Device Activity Report

Example

DEVICE AVG AVG AVG AVG AVG AVG

STORAGE DEV DEVICE VOLUME PAV LCU ACTIVITY RESP IOSQ CMR DB PEND DIS

GROUP NUM TYPE SERIAL RATE TIME TIME DLY DLY TIME TIM

9510 33909 HY9510 16H 0227 7217.70 2.3 0.0 0.7 0.0 0.9 0.

LCU 0227 7217.70 2.3 0.0 0.7 0.0 0.9 0.

Summary

HyperPAV has proven to be a superior solution for customers with IO demands for

market open and close. With HyperPAV customers approaching UCBs and alias limits

can benefit from the reduced number of UCBs and aliases needed.

ATS would like invite customers to take advantage of the UCB and Alias Analysis offering

to demonstrate the value of HyperPAV in your environment.

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Additional Reading and Reference Material

Understanding the Performance Implications of HyperPAVs, Dr. H. Pat Artis

http://www.perfassoc.com/publishedpapers.html

z/OS support of the IBM TotalStorage Enterprise Storage Server

http://domino.research.ibm.com/tchjr/journalindex.nsf/a3807c5b4823c53f8525656100632

4be/cd2d706d12b8861985256d67006afd28?OpenDocument

DS8000 Alias Analysis for HyperPAV AG Storage ATS Offering

http://w3-03.ibm.com/support/techdocs/atsmastr.nsf/WebIndex/FLASH10555

IBM System Storage DS8000 Series, Architecture and Implementation, SG24-6786-02

z/OS V1R8 MVS Initialization and Tuning Reference, SA22-7592-14

z/OS V1R8 MVS System Commands, SA22-7627-15

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