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DB2 UDB for z/OS Version 8 Performance Topics - IBM Redbooks

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Chapter 5. Availability and capacity<br />

enhancements<br />

Continuous availability is a major business requirement. New releases of <strong>DB2</strong> keep<br />

introducing enhancements to meet this need.<br />

5<br />

<strong>DB2</strong> V8 introduces new and enhanced function in this area.<br />

► System level point-in-time recovery: V8 provides enhanced backup and recovery<br />

capabilities at the <strong>DB2</strong> subsystem level or data sharing group level. The new BACKUP<br />

SYSTEM and RESTORE SYSTEM utilities rely on the new Fast Replication services of<br />

DFSMS in z/<strong>OS</strong> V1R5.<br />

► Automated space management: This feature potentially enhances availability <strong>for</strong> many<br />

<strong>DB2</strong> installations. <strong>DB2</strong> will adjust the size of the secondary extent, when extending the<br />

data set, in such a way that the maximum allowable data set size is reached be<strong>for</strong>e the<br />

maximum number of extents, avoiding out of space conditions.<br />

► Online schema: Online schema evolution allows <strong>for</strong> table space, table and index attribute<br />

changes while minimizing impact on availability.<br />

► Volatile table: Statistics <strong>for</strong> tables which can vary greatly in size can deviate completely at<br />

runtime from values used at bind time. Per<strong>for</strong>mance can benefit from favoring index<br />

access <strong>for</strong> these types of tables.<br />

► Index changes: Data-partitioned indexes, partitioning without a partitioning index, padded<br />

and not-padded indexes enhance indexing capabilities.<br />

► More availability enhancements: Other <strong>DB2</strong> V8 availability enhancements and also<br />

recent enhancements introduced via maintenance are discussed in this section.<br />

© Copyright <strong>IBM</strong> Corp. 2005. All rights reserved. 217

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