IMS Fundamentals - Availability

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Enhancing IMS Availability


Objectives

• See how Concurrent Copy can be used to increase IMS database availability

• Know and differentiate between XRF (Extended Recovery Facility) and RSR (Remote Site Recovery).

• Learn about Data Sharing among multiple IMS subsystems and how it evolved into IMS Parallel Sysplex Data Sharing.

• See how IMS Shared Queues and other IMS functions can use IBM Coupling Facilities to share information between IMS systems.

• Discover the features of the IMS Common Service Layer (CSL) Architecture and how CSL can aid in managing an IMSPLEX.

• Learn how the Operations Manager address space provides the ability to issue IMSPLEX-wide commands through the SPOC interface.


DFSMS Concurrent Copy Support

• DFSUDMT0 - Database Image Copy 2 Utility– Invokes DFSMSdss DUMP to create copy of data set– Can produce consistent (clean) or concurrent (fuzzy) image copy

• Clean image copy requires/DBR until logical copy completes• Fuzzy image copy does not require/DBR• To get fuzzy image copy of KSDS

DEFINE (ALTER) CLUSTER ..... BWO(TYPEIMS)– IMS database data sets supported

• HDAM, HIDAM, HISAM, DEDB• OSAM, ESDS, KSDS

– Will produce 1-4 copies• Two copies registered with DBRC at completion of DUMP• Additional copies can be available for shipment offsite


Typical IMS Failure & RecoveryProcessing Center End-User Activity

Problem occurs @%&*#!!%Problem detection No response Z Z ZOperational decisionProblem determination Phone HELP DeskFault isolation @%&*#!!% Z Z

Reconfiguration or repair Coffee Phone againRe-IPL of z/OS systemRestart of IMS/TMRe-synchronize databases @%&*#!!%Restart networkReconnect End-usersReenter lost work Where am I ?Resume What was I doing? Resume


NETWORK (WITH XRF SWITCH)

PRIMARYSESSIONS

BACKUPSESSIONS

VTAM1

IMS1

(ACT)IMS2

(ALT)

LOWERPRIORITY

WORKLOADISC LINK

(OPTIONAL)

IMSONLINE

LOGDATASETS

IMSDATABASEDATA SETS

zOS1 zOS2

LOG TRACK

UPDATESPASSIVECONNECTION

INTERACTIVE END USERS

VTAM2

Steady State: Before Takeover



OLD "ACTIVE" SESSIONS

PRIMARYSESSIONS

VTAM1

IMS1 (OLD ACT)

IMS2 (NEW ACT)

IMS ISC LINK

(OPTIONAL)

IMS

ONLINELOG

DATASETS


zOS1 zOS2

GET IN SYNC

DB BACKOUT AND RECOVERY


VTAM2

| X |

During Takeover



PRIMARYSESSIONS

VTAM1

VTAM2

IMS2(ACT)

zOS1 zOS2

UPDATES


LOGIMS

ONLINELOG

DATASETS


After Takeover



PRIMARYSESSIONS

BACKUPSESSIONS

IMS1

(ALT)

VTAM2

IMS2

(ACT)

LOWERPRIORITY

WORKLOAD IMSISC LINK

(OPTIONAL)

zOS1 zOS2

LOGTRACK

UPDATESPASSIVECONNECTION


IMS

ONLINELOG

DATASETS


VTAM1

Steady State: After Takeover


Remote Site Recovery

• RSR Database Support– Database Level Tracking (DLT)

• RSR provides remote database shadowing• Reduces service outage to minutes• Requires dedicated DASD for databases while tracking

– Recovery Level Tracking (RLT)• User must recover databases following a takeover• Service outage will be measured in hours• Does not require dedicated DASD for databases while tracking

• Level of support selectable by database• Level of support defined in DBRC RECONs and can be

changed dynamically


Data Sharing Definition

• “The DATA SHARING facility allows multiple application programs in different IMS and/or CICS subsystems to concurrently process common DL/I databases with full integrity.”

• DATABASE-LEVEL SHARING– DBRC controls used of database

• BLOCK-LEVEL DATA SHARING– IMS Resource Lock Manager (IRLM) provides “global” Program

Isolation (PI)

• IRLM, and IMS Data Sharing have been available since IMS 1.2 (about 1980)


USERTERMINAL

USERTERMINAL

MASTERTERMINAL

USERTERMINAL

z/OS

IMS/TM DBRC DLISAS IMS/BATCH

IMS/MPR

DL/I

AP

PL

APPL

MSGQUEUE RECON

IMSDB(S)

CORPORATEDATA BATCH

DB(S)

APPL

CICS

DL/I

Data Sharing Definition


DBRC Share-Level Options• DATABASE-LEVEL SHARING

– SHARELVL(0)• Guarantees EXCLUSIVE use

– SHARELVL(1)• 1 updater; multiple Read-Only (RO)• Multiple readers, RO and/or Read w/Integrity (RD)

• BLOCK-LEVEL DATA SHARING

– SHARELVL(2)• Multiple UP/RD/RO• Maximum 1 z/OS system image• INTRA-system, DBRC, one IRLM

– SHARELVL(3)• Multiple UP/RD/RO• MULTIPLE z/OS system images• INTER-system, two IRLMs, VTAM "connection"


z/OS 1 z/OS 2 z/OS 3

IMS2 IMS3

DBRC

MPRBMPIFP DBRC

MPRBMPIFP

RECON

IMS DBSOR

FP DEDB

SHARELVL(1)

OR

–ALL SUBSYSTEMS MAY "READ WITH INTEGRITY"

DL/I BATCH

READ-ONLYW/O INTEGRITY READ-ONLY

W/O INTEGRITY

IMS1

DBRC

UPDATER

Database-Level Sharing


z/OS 1

DBRC

OnlineS/S

DBRC

OnlineS/S

DBRC

ONE z/OS SYSTEM:

OnlineS/S Batch

RECON

IMS DBSOR

FP DEDB

SHARELVL(2)

IRLM

Intra-System Block-Level Data Sharing


ONLINES/S

DBRC

IRLM

VTAM

ONLINES/S

DBRC

IRLM

VTAM

RECON

IMS DBSOR

FP DEDB

SHARELVL(3)

z/OS 1 z/OS 2

Inter-System Block-Level Data Sharing


Data Sharing Summary

• Other Data Sharing subsystems could be:– IMS DBCTL– IMS TM– Off-Line Batch (DBBBATCH/DLIBATCH)– Selected IMS utilities, such as CIC

• IRLM is required for Block-Level Data Sharing• Increased system availability:

– More operational flexibility via separate subsystems– Failure isolation via separate subsystems


VTAM

IMS TM

MSG Queue

IMS DB

Lock Manager

z/OS

VTAM

IMS TM

MSG Queue

IMS DB

Lock Manager

z/OS

VTAM

IMS TM

MSG Queue

IMS DB

Lock Manager

z/OS

DB2

LocksDirectories

Coupling Facility

IMSDATA-BASE

DB2DATA-BASE

Allocationof

workstations

IMS DBData

Sharing

Easier access and management of enterprise IMS DB data

MSG

MSG

MSG

IMS in a Parallel Sysplex


N-Way Data Sharing

• IMS/ESA Version 5 allowed up to 32 IMS subsystems distributed among, at most, 32 z/OS images, in a z/OS sysplex, to share databases.– current limit is 64– Sharing across more than two z/OS images ("LPARs") requires the

use of the S/390 - z/OS Coupling Facility technology• IMS/ESA Version 5 introduced a new IRLM (Version 2.1)

– IRLM Version 2.1 can currently communicate with up to 63 other instances of IRLM Version 2.1, using Coupling Facility technology

– "Old" IRLM (Version 1.5) was discontinued with IMS Version 7• Data sharing is supported among all IMS versions

– Block level data sharing logic (what locks are obtained when) was not changed between IRLM V1.5 and V2.1


IMS A IMS B

Database

IRLM A IRLM BC Q S A C Q S B

OSAMCACHE

Structure

OSAMBlock X

CF

OSAM Caching


CF

IMS A IMS B

IRLM A IRLM BC Q S A C Q S B

D E D B

V S Oin Cache

Database

Shared VSO (Virtual Storage Option)


Coupling Facility

IMSASyste

m

IMSCSyste

m

IMSBSyste

m

IMSDSyste

m

N-Way DataSharing

Database

What happens when IMSA fails?

==> Answer: Its Locks are retained!!! <==

Impact of an IMS Failure with Data Sharing


IMS D

IMS C

IMS B

IMS A

SHAREDDATABASE

IMS A failedbut

UPDATE-LOCKsare held by CF for

this databaserestart

(/ERE & backout)of IMS A

If applications ofIMS B, IMS C or IMSD

request datalocked by IMS A

they will get U3303

(LOCK REJECT)

U3303

U3303

U3303

IMS Lock Reject - ABEND U3303


IRLM

IRLM

FDBR

CTL

MPRs

BMPs

DLI

DBRC

CF

LockStructur

es

Active IMS Fast DB Recovery

SharedDatase

ts

Shared Datsetsƒ OLDSƒ WADSƒ RDSƒ RECONƒ ACBLIBƒ MODBLKSƒ MODSTATDatabases

FDBR can be installed on same or

different z/os

ƒ FDBR Configuration

Fast Database Recovery (FDBR) in Sysplex


FDBRA

IMSA

z/os A

FDBRB

IMSB

z/os B

FDBRC

IMSC

z/os C

FDBRD

IMSD

z/os D

FDBRE

IMSE

z/os E

FDBR on same z/os as active IMS

Note:NOT recommended for production

FDBR Configuration: Sample 1


FDBRE

IMSA

z/os A

FDBRA

IMSB

z/os B F

DBRB

IMSC

z/os C

FDBRC

IMSD

z/os D

FDBRD

IMSE

z/os E

FDBR configured as a ring

Note:Best Configuration for production

FDBR Configuration: Sample 2


IMS AMSGQ

TX A1 LTERM

IMS BMSGQ

Shared

DB

TX B1 LTERM

IMS A

IMS B

SharedQueue

Structure

Shared

DB

MSGB1 MSGA1

CF

LTERMA LTERMB

processing

w/o w/

IMS C

IMS Shared Queues


A set of input and output message queues which can be shared by multiple IMSs in a Parallel Sysplex.

Coupling Facility

QUEUES

ListHeaders Messages

IMS2 IMS3IMS1

What are Shared Queues?


IMS3

TRANX queueis shared byall MPPsin any IMScapable ofprocessing it.

Output messagegoes on LTERMqueue for delivery by IMSwhich is in session withLTERMZ

Shared MSGQueue StructureCoupling Facility

LTERMZ

TRAN-Q RESPX LTERM-QTRANX

IMS2IMS1

IMS1MPP

IMS2MPP

IMS3MPP

IMS1MPP1

IMS2MPP1

IMS3MPP1

TRANX

RESPX

(1)

(2) (3)

(1)

MPP1 in IMS2 is first to ask for TRANX

Shared Message Queues - Example


Common CQS Data Sets

IMS2

Coupling Facility

IMS1

EMHQCKHPT MSGQ

CKHPT

MSGQCKHPT

EMHQCKHPTMSGQ

SRDS1EMHQSRDS1

MVSLOGLOGGER

SPILL

MVSLOG

MVSLOGLOGGER STAGING

MSGQ Logger Structure

EMHQ Logger Structure

MSGQ OFLW Structure

EMHQ OFLW Structure

OLDSMSGQ Primary Structure

EMHQ Primary Structure

LOGGER STAGING

IMS3

OLDS

OLDS

IMS V10

IMS V9

IMS V10

CQS1

LOGGER V9

LOGGER

CQS2

V9

Shared Queues Components


ƒ All IMSs in a Sysplex Environment are belonging to a Generic Resource Group

ƒ IMS-User logons to a Generic Resource Name for the IMS Sysplex

ƒ VTAM establishes a connection to a member of the group (e.q. IMSA)

IMS A IMS B IMS n

VTAMwith Generic Resource Support

CF

Coupling Facility

LOGON IMS

VTAM Generic Resource (VGR)


IMS A IMS B IMS n

VTAMwith Generic Resource Support

LOGON IMS

LU1 LU2 LU3 LU4

IMS B fails

User connected to LU1 oncemore has to logon to VTAM Resource Group

User/LU1 will be connected to a surviving IMS (not IMSB)

= Cloned Systems

CF Coupling Facility

User Impact with VGR


IMS2DBRC

CQS2

LOGR

CQS1

LOGR

VTAMTCP/IP

TRANSACTION

Network

IMS3DBRCIMS1

DBRC

VTAMTCP/IP

IMSCONNECT

XCF

LOGSMQ

OSAMVSAMSVSOLOCKVGR

MNPS

IMSplex

IMS Sysplex Components

• IMS uses many parallel sysplex functions to share resources in an IMSplex– Data sharing, shared queues– VTAM generic resources, multinode persistent sessions– Automatic restart management, XCF communications


IMS1

IMS3 IMS4

IMS2

Network

DBSMQ

Shared Resources

MTO

EndUser

SystemConsole

E-MCS

@DBR DB XYZ

/STA DB 18/STOP NODE

/STA TRAN

/DIS STATUS

AUTOMATION

Managing Shared IMS Resources

• But managing these resources became more difficult– Systems management functions needed to be more robust


The IMSplex

• Definition of an IMSplex– An IMSplex is a set of IMS address spaces that are working together

as a unit and are most likely running in a parallel sysplex with a common service layer (CSL)• Note: The IMSplex is not new, we're just now formalizing the term

– Examples of an IMSplex include ...• A set of IMS control regions without a CSL that are data sharing or

message queue sharing

• A set of IMS control regions without the CSL that are data sharing or message queue sharing with IMSs with a CSL

• A set of IMS control regions with a CSL that are data sharing or message queue sharing

• A single IMS control region with a CSL


Common Service Layer (CSL)

• The next step in IMS architectural evolution– Address spaces built using the Base Primitive Environment (BPE)

• Structured Call Interface (SCI)– IMSplex member registration– Communications between IMSplex members

• Operations Manager (OM)– IMSplex-wide command entry and response

• Resource Manager (RM)– Global resource and process management– VTAM terminal/user status recovery

– Enables systems management functions in IMSplex• Sysplex Terminal Management (STM)

– Uses SCI and RM• Single point of control (SPOC) and user-provided automation (AOP)

– Uses SCI and OM• Coordinated Online Change (Global Online Change)

– Uses SCI, OM, and RM• HALDB Online Reorganization (Online Reorg)

– Uses SCI and OM


SCI

DBRC

SCI

CommonQueueServer(CQS)

OperationsManager

(OM)

SCI

IMSControlRegion

SCI

ResourceManager

(RM)

SCI

StructuredCall

Interface

SCI

Online DBRCDBRC Batch UtilityBatch with DBRCUtility with DBRC

Global Online ChangeSysplex Terminal Management

CommunicationsAutomatic RECON Loss NotificationSPOC

Automation

MasterTerminal

End UserTerminal

SCICommunications

Automation

SPOC

New CSLaddress spaces

CF

CQS

SCI

IMS

CouplingFacility

New function

ResourceLOGRSMQ

OSAMVSAMSVSOIRLMVGR

CSL Architecture


IMSCTL

SCI

SCI

CQS

OM

SCI

IMSCTL

SCI

RMSCI

SCISCI

SCI

CQS

OM

SCI

RMSCI

SCISCI

SCI

CQS

OM

SCI

RMSCI

SCISCI

SCI

CQS

OM

SCI

RMSCI

SCISCI

CF

XCF

XCF

XCF XCF

SCI

SCI SCI

ResourceList Structure

LOGRList Structures

SMQList Structures

OSAMCache Structure

VSAMCache Structure

Shared VSOCache Structures

IRLMLock Structure

VGRList Structure

IMSCTL

SCI

IMSCTL

SCI

SCI

IMSplex Configuration

• In an IMSplex– All members share the same CF structures– Intra-IMSplex communications is implemented by SCI using XCF

across OS images


CSL Component – Operations Manager

• Operations Manager (OM)– Provides an API supporting common point of command entry

• Focal point for operations management and automation• Command responses from multiple IMSs are consolidated

– Provides the following services to members and clients of an IMSplex• Provide an API for IMS commands submitted from outside IMS

– Classic ("Type 1") IMS commands (/cmd ...)– New ("Type 2")IMSplex commands (QRY, INIT, TERM, DEL, UPD)

• Command registration to support any command processing client– Clients tell OM which commands it can process

• Command security – Perform authorization within OM - before sending to IMS– RACF or user-written command security exit

• Route commands to IMSplex members registered for the command• Consolidate command responses from individual IMSplex members into

a single response to present to the command originator


SPOC Features

• The SPOC application ...– Allows user to set preferences– Allows the user to specify shortcuts and set default command

parameters– Allows user specified grouping of IMSplex members– Allow the user to enter commands to one or more IMSs– Displays consolidated IMSplex and classic IMS command responses– Allows the user to sort IMSplex command response by column– Keep a history of commands– Allows the user to enter long commands


Unit Summary• Concurrent Copy can be used to increase IMS database

availability.• XRF (Extended Recovery Facility) and RSR (Remote Site

Recovery) are features that enhance IMS availability .• Parallel Sysplex allows up to 64 IMS subsystems to share

databases• Shared Message Queues allows all IMSs in a Parallel Sysplex

to share the same message queue• Shared VSO, OSAM Caching, and VTAM Generic Resources

are additional IMS functions that use IBM Coupling Facilities to share information between IMS systems.

• The IMS Common Service Layer (CSL) Architecture is a collection of new IMS Address Spaces that provide global functions that can aid in managing an IMSPLEX.

• The Operations Manager is a new CSL address space that provides the ability to issue IMSPLEX-wide commands through the SPOC interface

IMS Fundamentals - Availability

Technology

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