Top area of the window
The top area of the Table Space Statistics window shows general information
about the table space.
The columns in the window show both those statistics that were gathered at
the time of the explain, and those that currently exist in the system catalog
tables.
Rows in the Table Space Statistics window
The following information is shown:
- EXTENTSIZE
- The number of 4KB pages of table data that is written to each table space
container. (Note that when data fills multiple extents, the extents are
written to different containers in an alternating, or round robin,
way.)
- PREFETCHSIZE
- The number of 4KB pages that the database manager will prefetch for the
table space. Prefetching improves the performance of table sorts and
table scans, but may cause unneeded pages to be read into the buffer.
For more information, see the section on prefetching data into the buffer pool
in the Administration Guide.
- OVERHEAD
- The total overhead (in milliseconds) for a single random input or output
operation to the specified table space. The value includes controller
overhead, disk seek times, and latency times.
- TRANSFERRATE
- The time required to read a 4KB page from the specified table space (in
milliseconds).
- TBSPACETYPE
- The type of table space. The type can be a
database managed space (DMS) or a system managed
space (SMS).