RAID 1: mirroring

RAID 2: synchronized access with separate error correction disks

RAID 3: synchronized access with fixed parity disk

RAID 4: independent access with fixed parity disk

RAID 5: independent access with rotating parity

RAID 6: dual redundancy with rotating parity

Note that we still closely associate the terms volume and device because the mapping is fixed. A logical device now consists of those storage facility resources required to manage the data that is accessible to an ESCON device. This definition can also be extended to a SCSI logical unit in a disk data-sharing environment. The definition of the mapping between logical volumes and physical arrays of disks can be done by configuration tools at the level of the storage server by implementing the fixed mapping tables. Figure 22 on page 86 shows an example of RAID mapping: eight logical volumes onto four physical head disk assemblies (HDAs) in a RAMAC 3 drawer. Note that, while the logical volume view is still Extended Count Key Data (ECKD) architecture, the physical HDAs have a fixed block architecture (FBA). This flexible association disconnects the technology from the architectural implementation.

FIRST LOGICAL CYLINDER OF

VOL X

SECOND LOGICAL CYLINDER OF

VOL X

DISK1

VOL 0

VOL 1

VOL 2

VOL 3

VOL 4

VOL 5

VOL 6

VOL 7

VOL 0

VOL 1

DISK2

VOL 0

VOL 1

VOL 2

VOL 3

VOL 4

VOL 5

VOL 6

VOL 7

VOL 0

VOL 1

DISK3

VOL 0

VOL 1

VOL 2

VOL 3

VOL 4

VOL 5

VOL 6

VOL 7

PARITY

PARITY

DISK4

PARITY

PARITY

PARITY

PARITY

PARITY

PARITY

PARITY

PARITY

VOL 0

VOL 1

Figure 22. RAMAC3 Drawer Logical Volume Mapping

9.1.3 Log Structured File and SnapShot

The physical disk space is considered as a never-ending sequential space, called a log. New or updated data is placed at the end of the log, in the free area. Therefore, data is never updated in place; it is always written to a new place. Only the most recent copy of the data is valid, and a directory indicates the position of this copy. The track image is the update unit.

Every functional volume is defined as the most recent set of tracks. This concept offers two advantages:

• Timed evolutionary view of the data

86Storage Management with DB2 for OS/390

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Image 108
IBM 5655-DB2, 5695-DF1 manual Log Structured File and SnapShot, Timed evolutionary view of the data

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.