SysPlex

1. SysPlex -What’s the problem Problems are growing faster than uni-processor….1980’s Leads to SMP and loosely coupled Even faster than SMP and loosely coupled Disks -Issues SMP scalability, Disk thru-put -Need a High speed sharing capability with: Good bus bandwidth, low locking overhead, and good communication Bandwidth High/Continuous Availability

2. Base SysPlex The base sysplex is similar to a loosely coupled configuration: - More than one CPC (possibly an SMP) shares DASD and is managed by more than one MVS image. A sysplex is different from a loosely coupled configuration because: - There is a standard communication mechanism ( XCF) for system applications. - A more unified system image single console can manage all components

3. Base SysPlex • What base sysplex added: • -A standard way to communicate between systems (CTC links) • -The support for cluster data sets • -A common time source in the cluster

4. Parallel Sysplex • High performance communication and data sharing could be technically difficult. • With the Parallel Sysplex: • A new coupling technology gives high performance multi-system data sharing capability to authorized applications, such as subsystems. • Use of the coupling facility by subsystems,(e.g.IMS) provides: • - integrity and consistency of data throughout the entire sysplex. • - the capability of linking together many systems and providing • multisystem data sharing • Makes the sysplex platform ideal for parallel processing, particularly for • online transaction processing (OLTP) and decision support

5. Parallel Sysplex • What Parallel Sysplex Added • - high performance, multisystem data sharing across all the • systems. • - workloads can be dynamically balanced across systems with • new workload management functions. • - increased system capacity over loosely coupled and base sysplex • - ability to add incremental capacity to match workload growth • - increased system availability over loosely coupled and base sysplex • - better systems management than with the base sysplex via • An enhanced single-system image

6. Data Sharing Techniques - Single Server -Partitioning the Data -Sharing the Data between systems

7. Single Server Data Sharing - Advantage Simple, easy to understand Disadvantage Single point of Failure Capacity of 1 server may be a constraint e.g. response time, thru-put May be difficult to grow

8. Partitioning the Data - Advantage More CPU power to apply to situation Disadvantage May lose part of the database..partial failure May be hard to partition so the workload is balanced Thru-put and response time may be bad unless partitioning Is good Upgrades or increase in load may require re-partitioning Adding a processor probably requires re-partitioning

9. Sharing the data between 2 systems - Advantages Sharing the load, Possibly no single point of failure. Systems my grow incrementally -Disadvantages Lots of communication messages my impact performance Does not scale to many systems

10. Data Sharing using Parallel Sysplex • Data is managed as a Single system with multiple users • data sharing based on the coupling facility: • -makes it practical to have read/write data sharing among more than two systems. • -data management systems communicate so that they can directly share data • -No re-partitioning if you add another system • -No single point of failure

11. Parallel Sysplex Data Sharing Capabilities • - Storage is dynamically partitioned into structures • - Services manipulate data within the structures. • - Structure Types • > Cache structure - Supplies a mechanism called buffer invalidation to • ensure consistency of cached data. • Can also be used as a high-speed buffer for storing shared data • with common read/write access. • >List structure - Enables authorized applications to share data that is • organized in a set of lists, • For implementing shared queues and shared status information. • >Lock structure - Supplies shared and exclusive locking capability for • Serialization of shared resources down to a very small unit of data. • - Sysplex Timer – To provide a common time base for the Sysplex

12. Parallel Sysplex Data Sharing Capabilities • Lock structures- supply shared and exclusive locking. • Cache structure supplies invalidation to ensure consistency of cached data. • Can be used as a high-speed buffer for storing shared data with common read/write access. • Used by subsystems to provide buffer coherency across multiple systems • List structures. List structures enable applications lists for implementing functions such as shared work queues and shared status information. List entries can be s FIFO or LIFO, and access serialized or unserialized. • Timers. Allow sequencing events in multiple users. Example: Database restart needs to apply log records from several systems in the correct time sequence.

13. Subsystems that use the Sysplex - IMS – Hierarchical Data Base - DB2 – Relational Data base -CICS – Transaction Processing -VSAM – Index Access Method -RACF - Security -JES2 - Spooling - WLM - Work load manager

14. Coupling facility (CF) Sysplex Availability - Duplex CFs Structures can be duplexed across CFs, Failure of one CF, the other copy of the structure is used to satisfy all requests. A key component to provide fail safe capability (100% availability)