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

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

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

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

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

Data Sharing Techniques  - Single Server -Partitioning the Data -Sharing the Data between systems

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

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

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

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

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

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.

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

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)