IMS Plex and Shared Queues

IMS Plex and Shared QueuesJack PintoDavid SosaMarilene Noronha RoderIMS Silicon Valley laboratorySan Jose, California

IMS Latin America Road Show

October, 2009

2 IMS Latin America Road Show 2009

IMS – High Availability Configurations

IMS subsystem has multiple features to eliminate planned outages and minimize the impact of unplanned outages– Multiple cloned IMSs in Parallel Sysplex– Data sharing– Fast database recovery (FDBR) or– Extended Recovery facility (XRF) – not both– Automatic Restart Manager (ARM) support– Shared Queues– Online change– Common Service Layer (CSL)– Dynamic Resource Definition


Cloned IMSs– All IMSs can use a single system definition

– Definitions which must be unique can be redefined at execution time with runtime parameters

• For example, master and secondary terminal definitions

– With common definitions, all applications can run on any IMS

• Reduces impact of planned or unplanned outage

– Easier to roll maintenance across the IMSplex

IMS – High Availability Configuration



Data sharing– Every database is available

from every IMS• All IMS database types can

be shared, except MSDBs – Fast database recovery

(FDBR)• One per active IMS• Monitors active IMS data

sharing system (reads OLDS)

• In event of IMS or system failure

– Backs out inflight work– Releases IRLM retained

locks

IRLMIRLM

CF

DB

FDBR1

OLDS

IMS1


Automatic restart management (ARM)– Automatically restarts IMS after system or IMS failure– ERE required even with FDBR

• Resolve in-doubts with CICS and DB2 • Release database authorizations

– Supports all IMS address spaces (IMS, CSL, SQ, FDBR)

– Saves time frequently spent (wasted) thinking about what to do

– Can “group” subsystems to restart on same LPAR in event of system failure

• IMS, CICS, DB2, MQ (with IMS Adapter)



Shared queues– All IMSs queue input and output messages on shared queue

structures in Coupling Facility• Full function and fast path EMH

– All messages are available to all IMSs• Some exceptions (e.g., SERIAL transactions)

– Minimizes input queue times for transactions• If front-end IMS busy, back-end can schedule transaction

– In event of failure (System or IMS)• Users can reconnect to another IMS and continue work• High availability connectivity configuration makes reconnecting easy or

transparent– When used with CSL and Resource Manager

• Command and end-user status can follow user to new IMS



IMS Shared Queues

I MS I MS

DB2I MS

VTAM or TCP/ I P

End-userEnd-userEnd-user

RM OM

I MSI MS

SharedData Shared

Operations

SharedMessageQueues

Single image to end user!


Common Service Layer (CSL)– Structured Call Interface (SCI)

• Automatic RECON Loss Notification (ARLN)– Notifies all DBRCs when any one DBRC reconfigures RECONs– Each DBRC switches RECONs and deallocates

– Operations Manager• Single point of control for all IMSs• Required for Type-2 commands

– INIT OLC, INIT OLREORG– CREATE and DELETE– UPDATE resource attributes and status– QUERY resources and environment

• SCOPE(ALL) command support– Command processed on all IMSs



Common Service Layer (CSL) ...– Resource Manager

• Global online change– Coordinates PREPARE and COMMIT phases across all IMSs– All succeed or all fail

• Sysplex terminal management (STM)– Manage resources across IMSplex– Significant status follows user to another IMS

» Command status» End-user status (CONV, FP RESP, STSN)

• Global status (V10)– Status of MODBLKS resources maintained in Resource Structure

» Databases, programs, transactions, routing codes– Status known to all IMSs



Online change– Coordinated global online change (requires CSL)

• Add, change, delete resources• Switch libraries• All resources quiesced during part of process• Coordinated across all IMSs

– Member online change for ACBLIB (IMS V10 – requires CSL)• Add or change individual PSBs and DBDs • Update made directly to ACBLIB – no switch• Only affected resources are quiesced• Coordinated across all IMSs


Member OLC is discussed in more detail in Part 2.


Dynamic resource definition (DRD)– Dynamically create or delete resource definitions using Type-2

commands• CREATE, DELETE

– Databases (DDIR)– Programs (PDIR)– Transactions (SMB)– Routing Codes (RCTE)

– Dynamically update resource attributes using Type-2 command• UPDATE

– Same resource types– MSC definitions

– Online change process not required

DRD is discussed in moredetail in Part 2.



Rolling Maintenance IMSplex offer opportunity to roll maintenance through sysplex

without losing availability– Notify users of intent to shut down IMS1 (for example)– VTAM users log off and back on to IMS generic resource name

when convenient• VGR routes logon to IMS2 or IMS3 or ....

– TCP/IP users not affected• IMS Connect will always select available IMS

– Shutdown IMS1 – Restart IMS1 with new maintenance and /START DC– Repeat process for IMS2, IMS3, etc.

Works for IMS and system maintenance– May need two step process when migrating to new release of IMS

• Step 1 – roll pre-req maintenance to all IMSs• Step 2 – roll new IMS libraries through each IMS


The IMSplex Shared-Everything Environment

IMS1Environment

IMS2Environment

IMS4Environment

IMS3Environment

Network

DBSMQ

Shared Resources

Shared Operations

Looks like single image to end users!

I

M

S


The IMSplex Shared-Everything Environment

IMS1Environment

IMS2Environment

IMS4/CHE FREEZE

IMS3Environment

Network

DBSMQ

Shared Resources

Shared Operations

In case of planned or unplanned outage,user still has access to all the data and applications.

I

M

S


The Key To High Availability Minimize impact of unplanned

outages– Multiple images (more

baskets)– Less pervasive– Faster recovery– BE PREPARED

Eliminate planned outages– Rolling maintenance– Online resource definition

changes– Online database tools– Faster database tools

Technology

IMS Plex and Shared Queues