Spotlight on DB2 6.10 - User Guide

Description

Value

Auto Storage

This value indicates whether a table space was created as an automatic storage table space:

• Yes is shown if the table space was created with the MANAGED BY AUTOMATIC STORAGE clause.

• No is shown if the table space was created with containers that were provided explicitly.

Current Pool ID

The unique identifier of the buffer pool a tablespace is currently using. The identifier consists of an integer.

Direct Read Time (msec)

The amount of time spent on direct reads on a tablespace. Direct reads are used to read VARCHAR and LOB (large object) column data from disk to satisfy queries and to perform backups. Time is shown in milliseconds.

Direct Write Time (msec)

The amount of time spent on direct writes from a tablespace. Direct writes are used to write VARCHAR and LOB column data to disk to satisfy queries and to perform data loads and restores. Time is shown in milliseconds.

Extent Size

The extent size used by a table space. This is the number of pages of table data that are written to a container in the tablespace before the next container is used. Extent size cam be 4, 8, 16, or 32 kilobytes.

File System Caching

This value indicates whether a table space uses file system caching:

• Yes is shown if the table space uses file system caching.

• No is shown if the table space does not use file system caching.

  

Files Closed

The total number of database files closed on a tablespace since the last Spotlight refresh. Files are closed when an application reaches the maximum number of database files it can open for reads and writes into and out of the buffer pool. The maximum is set with the MAXFILOP configuration parameter.

Next Pool ID

The unique identifier for the buffer pool a tablespace will use the next time the database is started.

No Victim Buffer

The number of times a preselected victim buffer was not available for immediate use by an agent. When a suitable buffer is not available, an agent must search to find one. This value applies when the DB2_USE_ALTERNATE_PAGE_CLEANING registry variable is set to ON. If the value is high in relation to number of logical reads in the buffer pool, increasing the number of page cleaners helps ensure that enough preselected victim buffers are available for proactive page cleaning.

Pool Async Read Time (msec)

The amount of time spent on asynchronous reads into the buffer pool. Asynchronous page reads occur when prefetchers read data and index pages from the tablespace into the buffer pool before these pages are needed by a query.

Pool Async Write Time (msec)

The amount of time spent on asynchronous page writes to a tablespace. Asynchronous page writes occur when page cleaners or prefetchers write data and index pages from the buffer pool to disk in anticipation of the need for space in the buffer pool. These page writes are performed asynchronously (outside of query processing).

Prefetch Size

The maximum number of pages the prefetcher gets from disk at a single time. Automatic is shown if automatic prefetch size is enabled. Number of pages is shown if automatic prefetch size.

Rebalancer Mode

This value indicates whether a forward or reverse rebalance is in use for a DMS table space (it does not apply to SMS table spaces):

• No is shown if no rebalancing is in use.

• Forward is shown if the current rebalance process is adding space to a DMS table space.

• Reverse is shown if the current rebalance process is removing space from a DMS table space.

Resize Enabled

This value indicates whether automatic resizing is enabled for a DMS table space (it does not apply to SMS or automatic storage table spaces):  

• Yes is shown if automatic resizing is enabled.

• No is shown if automatic resizing is not enabled.

Tablespace ID

The unique identifier for a tablespace. The identifier consists of an integer.

Unread Prefetch Pages

The number of pages that the prefetcher read into the buffer pool that were not used. If the number is high, this is a sign that prefetchers are causing unnecessary I/O by reading in pages that will not be used.