10.4.1 Asynchronous Writes

DB2 writes the log records (the control intervals) from the output buffer to the active log data set when the number of log buffers used reaches the value the installation set for the WRITE THRESHOLD field of installation panel DSNTIPL; see Figure 40 on page 115. The application is not aware of these writes.

10.4.2 Synchronous Writes

Synchronous writes usually occur at commit time when an application has updated data. This write is called forcing the log, because the application must wait for DB2 to write the log buffers to disk before control is returned to the application. If the log data set is not busy, all log buffers are written to disk. If the log data set is busy, the requests are queued until it is freed.

10.4.3 Writing to Two Logs

If there are two logs (recommended for availability), the write to the first log, in general, must complete before the write to the second log begins. The first time a log control interval is written to disk, the write I/Os to the log data sets are done in parallel. However, if the same 4 KB log control interval is again written to disk, then the write I/Os to the log data sets must be done serially to prevent any possibility of losing log data in case of I/O errors occurring on both copies simultaneously. This method improves system integrity. I/O overlap in dual logging occurs whenever multiple log control intervals have to be written; for example, when the WRITE THRESHOLD value is reached, or when log records accumulate because of a log device busy condition

10.4.4 Two-Phase Commit Log Writes

IMS applications with DB2, and CICS and RRS applications with additional resources besides DB2 to manage, use two-phase commit protocol. Because they use two-phase commit, these applications force writes to the log twice, as shown in Figure 38 on page 113. The first write forces all the log records of changes to be written (if they have not been written previously because of the write threshold being reached). The second write writes a log record that takes the unit of recovery into an in-commit state.

112Storage Management with DB2 for OS/390

Page 133 Page 135
Page 134
Image 134
IBM 5655-DB2, 5695-DF1 manual Writing to Two Logs, Two-Phase Commit Log Writes
Page 133 Page 135

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.
Top Page Image Contents