In 11.4, “Monitoring and analysis tools for DB2” on page 295, we demonstrate how to monitor and analyze whether indicators in your environment show that a different table space type might improve performance. In 8.4, “SMS to DMS table space conversion” on page 188, we discuss how to convert SMS table spaces into DMS table spaces. Key points: The database manager supports different types of containers that come with different characteristics with respect to performance and administrative overhead. The database manager supports different types of table spaces that correspond to container types and come with different characteristics with respect to performance and administrative overhead. The type of a table space is determined when it is created; any change of the type afterwards requires a migration.
Prefetching and I/O servers As described in 2.1.2, “DB2 architecture overview” on page 29, prefetching deals with how the database manager proactively retrieves one or more pages from disk into some buffer pool in the expectation that they will be required by an application. Prefetching index and data pages into the buffer pool can help improve performance by reducing the I/O wait time. In addition, parallel I/O enhances prefetching efficiency, such as when data is spread over multiple disks. The database management system uses dedicated threads (in Windows operating system) response processes (in UNIX-based operating systems) to perform prefetching. While these prefetchers are used for asynchronous fetching of pages into buffer pools, the page cleaners analogously are used for asynchronous write of pages from buffer pool to disk when they are no longer needed. Prefetchers and page cleaners are also called I/O servers. The number of I/O servers that is used by the database management system can be adjusted to reflect the given database environment and the requirements of applications. Key points:
Prefetching is a built-in technique to minimize disk wait time for data read. I/O between buffer pool and disk in general is done asynchronously. I/O can be parallelized using multiple I/O servers. Parallelizing I/O might improve performance.
Chapter 2. Content Manager base products
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