records into the input buffer used by the reading process (such as a recovery job or a rollback).

From a performance point of view, it is always best for DB2 to obtain the log records from the output buffer. These accesses are reported by DB2 PM; see F in Figure 41 on page 118. The next fastest access for DB2 is the active log; see G in Figure 41. Access to the archive log is not desirable; it can be delayed for a considerable length of time. For example, tape drives may not be available, or a tape mount can be required. A zero value for A in Figure 41 indicates that the active logs are sized adequately.

10.5.1 Improving Log Read Performance

In this section we present some considerations on choices to improve log read performance.

Active Log Size

Active logs should be large enough to avoid reading the archives, especially during restart, rollback, and recovery. When data is backed out, performance is optimal if the data is available from the output buffer or from the active log. If the data is no longer available from the active log, the active log is probably too small. For information about sizing the active log data sets, see 10.5.2, “Active Log Size” on page 117.

Log Input Buffer

The default size for the input buffer is 60 KB. It is specified in the INPUT BUFFER field of installation panel DSNTIPL (see Figure 40 on page 115). The default value is recommended.

Avoid Device Contention

Avoid device contention on the log data sets. See the recommendation made in 10.4.5, “Improving Log Write Performance” on page 114.

Archive to Disk or Tape

If the archive log data set resides on disk, it can be shared by many log readers. In contrast, an archive on tape cannot be shared among log readers. Although it is always best to avoid reading archives altogether, if a process must read the archive, that process is serialized with anyone else who must read the archive tape volume. For example, every rollback that accesses the archive log must wait for any previous rollback work that accesses the same archive tape volume to complete.

Archiving to disk offers several advantages:

•Recovery times can be reduced by eliminating tape mounts and rewind time for archive logs kept on tape.

•Multiple RECOVER utilities can be run in parallel.

•DB2 log data can span a greater length of time than what is currently kept in your active log data sets.

•Need for tape drives during DB2 archive log creation is eliminated. If DB2 needs to obtain a tape drive on which to create the archive logs and it cannot allocate one, all activity will stop until DB2 can create the archive log data sets.

116Storage Management with DB2 for OS/390

Page 137 Page 139
Page 138
Image 138
IBM 5655-DB2, 5695-DF1 manual Improving Log Read Performance, Active Log Size, Log Input Buffer, Avoid Device Contention
Page 137 Page 139

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