|PostgreSQL Reference Manual - Volume 3 - Server Administration Guide|
by The PostgreSQL Global Development Group
Paperback (6"x9"), 204 pages
RRP £13.95 ($24.95)
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4.4.2 Free Space Map
These parameters control the size of the shared free space
map, which tracks the locations of unused space in the database.
An undersized free space map may cause the database to consume
increasing amounts of disk space over time, because free space that
is not in the map cannot be re-used; instead PostgreSQL
will request more disk space from the operating system when it needs
to store new data.
The last few lines displayed by a database-wide
command can help in determining if the current settings are adequate.
NOTICE message is also printed during such an operation
if the current settings are too low.
Increasing these parameters may cause PostgreSQL
to request more
System V shared
memory than your operating system's default configuration
allows. See section 3.4.1 Shared Memory and Semaphores for information on how to
adjust those parameters, if necessary.
Sets the maximum number of disk pages for which free space will
be tracked in the shared free-space map. Six bytes of shared memory
are consumed for each page slot. This setting must be at least
max_fsm_relations. The default is chosen by initdb depending on the amount of available memory, and can range from 20k to 200k pages. This parameter can only be set at server start.
- Sets the maximum number of relations (tables and indexes) for which free space will be tracked in the shared free-space map. Roughly seventy bytes of shared memory are consumed for each slot. The default is one thousand relations. This parameter can only be set at server start.
|ISBN 0954612043||PostgreSQL Reference Manual - Volume 3 - Server Administration Guide||See the print edition|