BSAM, QSAM, and BPAM Support of zHPF

Irma T. Flores-Mendoza irmafm@us.ibm.com

IBM Corporation

Wednesday, August 8, 2012, 9:30 AM to 10:30 AMSession Number 11980

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Thanks to the people that contributed to this line item and this presentation

• Lyle Merithew

• Sue Candelaria

• John Paveza

• Maya Kalavathibai• Dale Riedy

• Harry Yudenfriend

• Aldo Paolo Dondi Diaz

• Yan Xu

• Lou Ricci

• Matthew Craig

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Session objective

• Explain how BSAM, QSAM, and BPAM achieve better performance with zHPF architecture than with FICON architecture

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Table of Contents

1. BSAM, QSAM, and BPAM (SAM) Support of zHPF2. SAM Support of zHPF: Installation Pre-requisites3. SAM Support of zHPF: Hardware Dependencies4. Performance differences between Command Mode BSAM/QSAM

and Transport Mode BSAM/QSAM5. SAM I/O Execution Flow – Front End Processing6. SAM I/O Execution Flow – Back End Processing7. A CCW Channel Program – Command Mode ECKD8. A zHPF Channel Program – Transport Mode ECKD9. A Command Mode FICON Exchange Pair10. A Transport Mode Exchange (zHPF)11. A Command Mode Information Unit (FICON IU)12. A Transport Mode Information Unit (zHPF IU)

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BSAM, QSAM, and BPAM (SAM) Support of zHPF

• BSAM - Basic Sequential Access Method• QSAM - Queued Sequential Access Method• BPAM - Basic Partitioned Access Method

• "Access methods are identified primarily by the data set organization" [z/OS DFSMS Using Data Sets, p.4]. BSAM and QSAM work with Physical Sequential data sets. And the BPAM zHPF support was implemented for sequentially accessing the member records of PDSs.

• BSAM, QSAM, and BPAM support of zHPF was implemented for sequential access (SAM) of non-Extended Format data records.

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SAM Support of zHPF: Installation Pre-requisites

• zHPF is enabled system wide (UCBFCX bit of the UCB Common Extension is set to ON) via:• the option ZHPF=YES of the IECIOSxx member of PARMLIB,

or• via the SETIOS ZHPF=YES command.

• zHPF is enabled for SAM (DFASAMHPF bit is set to ON) via:• the option SAM_USE_HPF(YES) of the IGDSMSxx member

of PARMLIB, or• via the SETSMS SAM_USE_HPF=YES command.

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SAM Support of zHPF: Hardware Dependencies

• DS8000 dependency: zHPF Phase 1 microcode level as specified in the Enterprise Disk Attachment Specification PCR 7030, FCR No.746 “zHPF Updates for QSAM/BSAM”:• Enterprise Disk DS8700 microcode Release 6.2 or • Enterprise Disk DS8800 microcode Release 6.2

• Channel Subsystem dependency:• z10 and z196 GA-1: Required ODT fix for Y4164 provided in

Bundle 6A in D93G:• Ficon Express8s level 0.20• Ficon Express8 level A.4E• Ficon Express4 level 5.4D

• z196 GA-2: Required zHPF Incorrect Length Facility

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Yan Xu, Performance Analyst

IBM Systems & Technology Group, Systems Hardware Development

Performance Slide #1: Bandwidth of BSAM/QSAM Reads

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Aldo Paolo Dondi Diaz, Software Performance Analyst

IBM Systems & Technology Group, Systems Hardware Development

Performance Slide #2: Elapsed Time of BSAM Reads

-28.45%

-10.98%

-13.85% -17.31% -0.39%

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Yan Xu, Performance Analyst

IBM Systems & Technology Group, Systems Hardware Development

Performance Slide #3: Bandwidth of BSAM/QSAM Writes

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Aldo Paolo Dondi Diaz, Software Performance Analyst

IBM Systems & Technology Group, Systems Hardware Development

Performance Slide #4: Elapsed Time of BSAM Writes

-36.07%

-34.23%-41.58% -37.48% -1.03%

SAM I/O Execution Flow – Front End Processing

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SAM Channel Program

in the SAMBX

I/Obuffers

Userprogram

SAM code

IOS

EXCPVR

DS8KControl Unit

SVC 114 (0A72)PFX/SIO

GET, PUT,READ, WRITE,etc.

SSCH

CPS/SIO exit

SAM I/O Execution Flow – Back End Processing

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SAM Channel Program

in the SAMBX

I/Obuffers

Userprogram

SAM code

IOS

EXCPVR

DS8KControl Unit

ABE/CHE

ERP

FLIH

I/O Interrupt

SLIH

A CCW Channel Program – Command Mode ECKD

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CCW

CCW

CCW

...

Command Address0 8 31

Flags Byte CountReserved32 40 48 63

Format 0 CCW

Command Flags Byte Count0 8 16 31

Address32 63

Format 1 CCW

A zHPF Channel Program – Transport Mode ECKD

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TCWTCW

TIDAL TIDAL Data Data

TCCB

TCA HeaderTCA Header

DCWs and control data

DCWs and control data

TCA TrailerTCA Trailer

TSB

TSB

TCW may also point directly to data

I/O completion info, sense data and measurement statistics

Commands and control data/parameters

User data to be written or buffer for data to be read

TCCB may also be pointed to by TIDAL

A Command Mode FICON Exchange Pair

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Prefix Cmd + 64 bytesRead (4k)

Status Accept

Read (4k)

Read (4k)

Read (4k)

Cmd Resp

Data (4k) + CRC

Data (4k) + CRC

Data (4k) + CRCData (4k) + CRC

Status

Channel to Control Unit Control Unit to Channel

Total Commands 5 N/A

Exchanges 1 1

Sequences 6 6

Frames 6 14

CRC Generate / Check 5 5

A Transport Mode Exchange (zHPF)

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Channel to Control Unit Control Unit to Channel

Total Commands 2 or 5 N/A

Exchanges 1 1 (same one)

Sequences 1 2

Frames 1 10

CRC Generate / Check 1 1

Prefix + 64 byes of prefix data +

Read (4k) 4 times (LRE Intent Count) Data (16k) + CRC

Status

Channel to CU in Ficon Mode

CU to Channel in Ficon Mode

Total Channel To CU in zHPF Mode

CU to Channel in zHPF Mode

Total % Reduction in zHPF Mode

Exchanges 1 1 2 1 1 1 50

Sequences 6 6 12 1 2 3 75

Frames 6 14 20 1 10 11 45

CRC Gen / Check

5 5 10 1 1 2 80

A Command Mode Information Unit (FICON IU)

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3 Frame IU to transfer 4K of data

SOF Header Data (2016 Bytes) CRC EOFFicon Header

SOF Header Data (2048 Bytes) CRC EOF

SOF Header Ficon CRC CRC EOFData (32 bytes)

A Transport Mode Information Unit (FICON IU)

9 Frame IU to transfer 16K of data

SOF Header Data (2016 Bytes) CRC EOFzHPF Header

SOF Header Data (2048 Bytes) CRC EOF

SOF Header zHPF CRC CRC EOFData (8 bytes)

SOF Header Data (2048 Bytes) CRC EOF

SOF Header Data (2048 Bytes) CRC EOF

SOF Header Data (2048 Bytes) CRC EOF

SOF Header Data (2048 Bytes) CRC EOF

SOF Header Data (2048 Bytes) CRC EOF

SOF Header Data (2048 Bytes) CRC EOF

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Conclusion

• BSAM, QSAM, and BPAM achieve better performance with zHPF architecture than with FICON architecture due to the characteristics of the zHPF architecture, which include:• Less number of exchanges and sequences (IUs) – less

hardware resources, less ACC IUs• Different method of packaging commands (many frames vs.

single frame) – different methods of processing the commands

• Larger maximum IU payload size, less number of exchanges for larger blocks – FICON:8k vs. zHPF:64k

• Less number of frames over the wire – less overall connect and transmit time

Thank you

Irma T. Flores-Mendoza irmafm@us.ibm.com

Wednesday, August 8, 2012, 9:30 AM to 10:30 AMSession Number 11980: BSAM, QSAM, and BPAM Support of zHPF