traditional disaster recovery, is that each software subsystem (CICS, IMS, DB2, VSAM, and others) has its own recovery technique. Because an application is typically made up of multiple software subsystems, it is impossible to get a time-consistent backup across all subsystems unless the application is stopped, which impacts availability. Please note that backups are still required in a remote copy environment.

Duplication can be done on the secondary server either synchronously or asynchronously with the primary server update. The IBM 3990 open extended architecture defines peer-to-peer remote copy (PPRC) for synchronous environments and extended remote copy (XRC) for asynchronous environments. To provide an operational disaster recovery solution, data consistency is mandatory for secondary remote copy volumes should any event occur to the primary, the secondary, or to links between primary and secondary. Continuous availability of the primary site is also mandatory when secondary site outage occurs. For consistency reasons, we recommend choosing only one remote copy technique, synchronous or asynchronous, for a given environment.

9.5.4.1 PPRC

PPRC allows two disk storage servers to directly communicate with each other through ESCON links. The storage servers can be sited up to 43 km apart. The remote copies are established between two disk volumes. Once the pairs are synchronized, the storage servers maintain the copies by applying all updates to both volumes. Updates must be received at both storage servers before the I/O is posted as complete to the application making PPRC operation synchronous. Figure 28 on page 96 shows the PPRC data flow (where SP stands for Storage Path).

 

4

 

3

 

 

 

to/from remote controller

2

1

 

 

 

 

 

1. Write to local cache and NVS

 

 

 

2. Channel End - channel is free

 

 

 

3. Write to remote cache and NVS

 

 

 

4. Device End upon acknowledgment

 

 

 

Notes:

 

 

 

- Steps 3 and 4 are disconnect time

 

 

 

SP is busy

 

 

1

- Steps 1 through 4 are service time

 

 

UCB is busy

 

 

 

CACHE

 

 

NVS

Figure 28. Profile of a PPRC Write

PPRC operations are entirely at the disk volume level. Write sequence consistency is preserved by the updates being propagated to the second site in real time. Databases that are spread across multiple volumes may be unrecoverable if a rolling disaster causes the secondary volumes to be at an inconsistent level of updates. A rolling disaster is one where various components fail in sequence. For example, if a data volume failed to update its secondary, yet the corresponding log update was copied to the secondary, this would result in a secondary copy of the data that is inconsistent with the primary copy. The

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IBM 5655-DB2, 5695-DF1 manual Profile of a Pprc Write
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5695-DF1, 5655-DB2 specifications

IBM 5655-DB2 and 5695-DF1 are significant components within the IBM software ecosystem, predominantly focusing on data management and integration solutions. These offerings cater primarily to enterprise environments that require robust database management systems and associated frameworks to maintain and manipulate data efficiently.

IBM 5655-DB2 is a well-known relational database management system (RDBMS) that excels in managing large volumes of structured data. Its architecture is designed to support high availability, scalability, and performance, crucial for businesses operating in today’s data-driven world. Some of its main features include advanced indexing capabilities, support for complex queries, and dynamic workload management. Additionally, it provides strong concurrency controls, which enable multiple users to access and manipulate data simultaneously without compromising data integrity.

One of the key characteristics of DB2 is its support for various data types, including JSON and XML, making it versatile for modern applications that generate data in diverse formats. It also features robust security mechanisms to protect sensitive data, aligning with compliance standards across industries. Integration with analytics tools further allows businesses to derive insights from their data, enhancing decision-making processes.

On the other hand, IBM 5695-DF1, also known as the InfoSphere DataStage, is a powerful data integration tool that facilitates the extraction, transformation, and loading (ETL) of data from various sources to target systems. It empowers organizations to streamline their data flows, ensuring that clean, consistent information is available for analysis and operational use. Key features of 5695-DF1 include a user-friendly graphical interface that enhances developer productivity and a rich set of connectors for numerous data sources, enabling seamless data integration.

DataStage also supports real-time data integration, allowing businesses to keep their data synchronized across multiple platforms. Its parallel processing capabilities dedicatedly optimize performance, enabling organizations to handle vast datasets efficiently. It incorporates data quality tools that help in validating and cleansing data before it is used for decision-making processes.

Both IBM 5655-DB2 and 5695-DF1 are part of a broader strategy to accommodate the evolving landscape of data management. Businesses leverage these technologies to enhance their data architectures, fostering agility and competitive advantage in their respective markets. Their integration capabilities, along with a focus on security and scalability, position them as vital assets in modern enterprise environments. Whether managing critical data within a database or ensuring seamless data flow across systems, these IBM offerings provide a comprehensive approach to handling complex data challenges.
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