+ linkend="vacuum-for-wraparound"/> for more information.
+
+
+
-
- autovacuum_max_workers (integer)
-
-
autovacuum_max_workers configuration parameter-
-
-
- Specifies the maximum number of autovacuum processes (other than the
- autovacuum launcher) that may be running at any one time. The default
- is three. This parameter can only be set in the
- postgresql.conf file or on the server command line.
-
- Note that a setting for this value which is higher than
- will have no effect,
- since autovacuum workers are taken from the pool of slots established
- by that setting.
-
-
-
+
+ autovacuum_worker_slots (integer)
+
+
autovacuum_worker_slots configuration parameter+
+
+
+ Specifies the number of backend slots to reserve for autovacuum worker
+ processes. The default is typically 16 slots, but might be less if
+ your kernel settings will not support it (as determined during initdb).
+ This parameter can only be set at server start.
+
+ When changing this value, consider also adjusting
+ .
+
+
+
-
- autovacuum_naptime (integer)
-
-
autovacuum_naptime configuration parameter-
-
-
- Specifies the minimum delay between autovacuum runs on any given
- database. In each round the daemon examines the
- database and issues VACUUM and ANALYZE commands
- as needed for tables in that database.
- If this value is specified without units, it is taken as seconds.
- The default is one minute (1min).
- This parameter can only be set in the postgresql.conf
- file or on the server command line.
-
-
-
+
+ autovacuum_max_workers (integer)
+
+
autovacuum_max_workers configuration parameter+
+
+
+ Specifies the maximum number of autovacuum processes (other than the
+ autovacuum launcher) that may be running at any one time. The default
+ is 3. This parameter can only be set in the
+ postgresql.conf file or on the server command line.
+
+ Note that a setting for this value which is higher than
+ will have no effect,
+ since autovacuum workers are taken from the pool of slots established
+ by that setting.
+
+
+
- ">
- autovacuum_vacuum_threshold (integer)
-
-
autovacuum_vacuum_threshold- <secondary>configuration parameter>
- term>
- m>
- >
- Specifies the minimum number of updated or deleted tuples needed
- to trigger a VACUUM in any one table.
- The default is 50 tuples.
- This parameter can only be set in the postgresql.conf
- file or on the server command line;
- but the setting can be overridden for individual tables by
- changing table storage parameters.
-
-
-
+ ">
+ autovacuum_naptime (integer)
+
+
autovacuum_naptime configuration parameter+ </indexterm>
+ term>
+ m>
+ Specifies the minimum delay between autovacuum runs on any given
+ database. In each round the daemon examines the
+ database and issues VACUUM and ANALYZE commands
+ as needed for tables in that database.
+ If this value is specified without units, it is taken as seconds.
+ The default is one minute (1min).
+ This parameter can only be set in the postgresql.conf
+ file or on the server command line.
+
+
+
-
- autovacuum_vacuum_insert_threshold (integer)
-
-
autovacuum_vacuum_insert_threshold- configuration parameter
-
-
-
- Specifies the number of inserted tuples needed to trigger a
- VACUUM in any one table.
- The default is 1000 tuples. If -1 is specified, autovacuum will not
- trigger a VACUUM operation on any tables based on
- the number of inserts.
- This parameter can only be set in the postgresql.conf
- file or on the server command line;
- but the setting can be overridden for individual tables by
- changing table storage parameters.
-
-
-
+
+ autovacuum_vacuum_threshold (integer)
+
+
autovacuum_vacuum_threshold+ configuration parameter
+
+
+
+ Specifies the minimum number of updated or deleted tuples needed
+ to trigger a VACUUM in any one table.
+ The default is 50 tuples.
+ This parameter can only be set in the postgresql.conf
+ file or on the server command line;
+ but the setting can be overridden for individual tables by
+ changing table storage parameters.
+
+
+
-
- autovacuum_analyze_threshold (integer)
-
-
autovacuum_analyze_threshold- configuration parameter
-
-
-
- Specifies the minimum number of inserted, updated or deleted tuples
- needed to trigger an ANALYZE in any one table.
- The default is 50 tuples.
- This parameter can only be set in the postgresql.conf
- file or on the server command line;
- but the setting can be overridden for individual tables by
- changing table storage parameters.
-
-
-
+
+ autovacuum_vacuum_insert_threshold (integer)
+
+
autovacuum_vacuum_insert_threshold+ configuration parameter
+
+
+
+ Specifies the number of inserted tuples needed to trigger a
+ VACUUM in any one table.
+ The default is 1000 tuples. If -1 is specified, autovacuum will not
+ trigger a VACUUM operation on any tables based on
+ the number of inserts.
+ This parameter can only be set in the postgresql.conf
+ file or on the server command line;
+ but the setting can be overridden for individual tables by
+ changing table storage parameters.
+
+
+
-
- autovacuum_vacuum_scale_factor (floating point)
-
-
autovacuum_vacuum_scale_factor- configuration parameter
-
-
-
- Specifies a fraction of the table size to add to
- autovacuum_vacuum_threshold
- when deciding whether to trigger a VACUUM.
- The default is 0.2 (20% of table size).
- This parameter can only be set in the postgresql.conf
- file or on the server command line;
- but the setting can be overridden for individual tables by
- changing table storage parameters.
-
-
-
+
+ autovacuum_analyze_threshold (integer)
+
+
autovacuum_analyze_threshold+ configuration parameter
+
+
+
+ Specifies the minimum number of inserted, updated or deleted tuples
+ needed to trigger an ANALYZE in any one table.
+ The default is 50 tuples.
+ This parameter can only be set in the postgresql.conf
+ file or on the server command line;
+ but the setting can be overridden for individual tables by
+ changing table storage parameters.
+
+
+
- _scale_factor">
- autovacuum_vacuum_insert_scale_factor (floating point)
-
-
autovacuum_vacuum_insert_scale_factor
- configuration parameter
-
-
-
- Specifies a fraction of the table size to add to
- autovacuum_vacuum_insert_threshold
- when deciding whether to trigger a VACUUM.
- The default is 0.2 (20% of table size).
- This parameter can only be set in the postgresql.conf
- file or on the server command line;
- but the setting can be overridden for individual tables by
- changing table storage parameters.
-
-
-
+ _scale_factor">
+ autovacuum_vacuum_scale_factor (floating point)
+
+
autovacuum_vacuum_scale_factor
+ configuration parameter
+
+
+
+ Specifies a fraction of the table size to add to
+ autovacuum_vacuum_threshold
+ when deciding whether to trigger a VACUUM.
+ The default is 0.2 (20% of table size).
+ This parameter can only be set in the postgresql.conf
+ file or on the server command line;
+ but the setting can be overridden for individual tables by
+ changing table storage parameters.
+
+
+
- _scale_factor">
- autovacuum_analyze_scale_factor (floating point)
-
-
autovacuum_analyze_scale_factor
- configuration parameter
-
-
-
- Specifies a fraction of the table size to add to
- autovacuum_analyze_threshold
- when deciding whether to trigger an ANALYZE.
- The default is 0.1 (10% of table size).
- This parameter can only be set in the postgresql.conf
- file or on the server command line;
- but the setting can be overridden for individual tables by
- changing table storage parameters.
-
-
-
+ _scale_factor">
+ autovacuum_vacuum_insert_scale_factor (floating point)
+
+
autovacuum_vacuum_insert_scale_factor
+ configuration parameter
+
+
+
+ Specifies a fraction of the table size to add to
+ autovacuum_vacuum_insert_threshold
+ when deciding whether to trigger a VACUUM.
+ The default is 0.2 (20% of table size).
+ This parameter can only be set in the postgresql.conf
+ file or on the server command line;
+ but the setting can be overridden for individual tables by
+ changing table storage parameters.
+
+
+
-
- autovacuum_freeze_max_age (integer)
-
-
autovacuum_freeze_max_age- configuration parameter
-
-
-
- Specifies the maximum age (in transactions) that a table's
- pg_class.relfrozenxid field can
- attain before a VACUUM operation is forced
- to prevent transaction ID wraparound within the table.
- Note that the system will launch autovacuum processes to
- prevent wraparound even when autovacuum is otherwise disabled.
-
+
+ autovacuum_analyze_scale_factor (floating point)
+
+
autovacuum_analyze_scale_factor+ configuration parameter
+
+
+
+ Specifies a fraction of the table size to add to
+ autovacuum_analyze_threshold
+ when deciding whether to trigger an ANALYZE.
+ The default is 0.1 (10% of table size).
+ This parameter can only be set in the postgresql.conf
+ file or on the server command line;
+ but the setting can be overridden for individual tables by
+ changing table storage parameters.
+
+
+
- Vacuum also allows removal of old files from the
- pg_xact subdirectory, which is why the default
- is a relatively low 200 million transactions.
- This parameter can only be set at server start, but the setting
- can be reduced for individual tables by
- changing table storage parameters.
- For more information see .
-
-
-
+
+ autovacuum_freeze_max_age (integer)
+
+
autovacuum_freeze_max_age+ configuration parameter
+
+
+
+ Specifies the maximum age (in transactions) that a table's
+ pg_class.relfrozenxid field can
+ attain before a VACUUM operation is forced
+ to prevent transaction ID wraparound within the table.
+ Note that the system will launch autovacuum processes to
+ prevent wraparound even when autovacuum is otherwise disabled.
+
-
- autovacuum_multixact_freeze_max_age (integer)
-
-
autovacuum_multixact_freeze_max_age- configuration parameter
-
-
-
- Specifies the maximum age (in multixacts) that a table's
- pg_class.relminmxid field can
- attain before a VACUUM operation is forced to
- prevent multixact ID wraparound within the table.
- Note that the system will launch autovacuum processes to
- prevent wraparound even when autovacuum is otherwise disabled.
-
+ Vacuum also allows removal of old files from the
+ pg_xact subdirectory, which is why the default
+ is a relatively low 200 million transactions.
+ This parameter can only be set at server start, but the setting
+ can be reduced for individual tables by
+ changing table storage parameters.
+ For more information see .
+
+
+
- Vacuuming multixacts also allows removal of old files from the
- pg_multixact/members and pg_multixact/offsets
- subdirectories, which is why the default is a relatively low
- 400 million multixacts.
- This parameter can only be set at server start, but the setting can
- be reduced for individual tables by changing table storage parameters.
- For more information see .
-
-
-
+
+ autovacuum_multixact_freeze_max_age (integer)
+
+
autovacuum_multixact_freeze_max_age+ configuration parameter
+
+
+
+ Specifies the maximum age (in multixacts) that a table's
+ pg_class.relminmxid field can
+ attain before a VACUUM operation is forced to
+ prevent multixact ID wraparound within the table.
+ Note that the system will launch autovacuum processes to
+ prevent wraparound even when autovacuum is otherwise disabled.
+
-
- autovacuum_vacuum_cost_delay (floating point)
-
-
autovacuum_vacuum_cost_delay- configuration parameter
-
-
-
- Specifies the cost delay value that will be used in automatic
- VACUUM operations. If -1 is specified, the regular
- value will be used.
- If this value is specified without units, it is taken as milliseconds.
- The default value is 2 milliseconds.
- This parameter can only be set in the postgresql.conf
- file or on the server command line;
- but the setting can be overridden for individual tables by
- changing table storage parameters.
-
-
-
+ Vacuuming multixacts also allows removal of old files from the
+ pg_multixact/members and pg_multixact/offsets
+ subdirectories, which is why the default is a relatively low
+ 400 million multixacts.
+ This parameter can only be set at server start, but the setting can
+ be reduced for individual tables by changing table storage parameters.
+ For more information see .
+
+
+
-
- autovacuum_vacuum_cost_limit (integer)
-
-
autovacuum_vacuum_cost_limit- configuration parameter
-
-
-
- Specifies the cost limit value that will be used in automatic
- VACUUM operations. If -1 is specified (which is the
- default), the regular
- value will be used. Note that
- the value is distributed proportionally among the running autovacuum
- workers, if there is more than one, so that the sum of the limits for
- each worker does not exceed the value of this variable.
- This parameter can only be set in the postgresql.conf
- file or on the server command line;
- but the setting can be overridden for individual tables by
- changing table storage parameters.
-
-
-
+
+ autovacuum_vacuum_cost_delay (floating point)
+
+
autovacuum_vacuum_cost_delay+ configuration parameter
+
+
+
+ Specifies the cost delay value that will be used in automatic
+ VACUUM operations. If -1 is specified, the regular
+ value will be used.
+ If this value is specified without units, it is taken as milliseconds.
+ The default value is 2 milliseconds.
+ This parameter can only be set in the postgresql.conf
+ file or on the server command line;
+ but the setting can be overridden for individual tables by
+ changing table storage parameters.
+
+
+
-
+
+ autovacuum_vacuum_cost_limit (integer)
+
+
autovacuum_vacuum_cost_limit+ configuration parameter
+
+
+
+ Specifies the cost limit value that will be used in automatic
+ VACUUM operations. If -1
+ is specified (which is the default), the regular
+ value will be used. Note that
+ the value is distributed proportionally among the running autovacuum
+ workers, if there is more than one, so that the sum of the limits for
+ each worker does not exceed the value of this variable.
+ This parameter can only be set in the postgresql.conf
+ file or on the server command line;
+ but the setting can be overridden for individual tables by
+ changing table storage parameters.
+
+
+
+
+
+
+
+
+
Cost-based Vacuum Delay
+
+ During the execution of
+ and
+ commands, the system maintains an
+ internal counter that keeps track of the estimated cost of the
+ various I/O operations that are performed. When the accumulated
+ cost reaches a limit (specified by
+ vacuum_cost_limit), the process performing
+ the operation will sleep for a short period of time, as specified by
+ vacuum_cost_delay. Then it will reset the
+ counter and continue execution.
+
+
+ The intent of this feature is to allow administrators to reduce
+ the I/O impact of these commands on concurrent database
+ activity. There are many situations where it is not
+ important that maintenance commands like
+ VACUUM and ANALYZE finish
+ quickly; however, it is usually very important that these
+ commands do not significantly interfere with the ability of the
+ system to perform other database operations. Cost-based vacuum
+ delay provides a way for administrators to achieve this.
+
+
+ This feature is disabled by default for manually issued
+ VACUUM commands. To enable it, set the
+ vacuum_cost_delay variable to a nonzero
+ value.
+
+
+
+
+ vacuum_cost_delay (floating point)
+
+
vacuum_cost_delay configuration parameter+
+
+
+ The amount of time that the process will sleep when the cost
+ limit has been exceeded. If this value is specified without
+ units, it is taken as milliseconds. The default value is
+ 0, which disables the cost-based vacuum delay
+ feature. Positive values enable cost-based vacuuming.
+
+
+ When using cost-based vacuuming, appropriate values for
+ vacuum_cost_delay are usually quite small, perhaps
+ less than 1 millisecond. While vacuum_cost_delay
+ can be set to fractional-millisecond values, such delays may not be
+ measured accurately on older platforms. On such platforms,
+ increasing VACUUM's throttled resource consumption
+ above what you get at 1ms will require changing the other vacuum cost
+ parameters. You should, nonetheless,
+ keep vacuum_cost_delay as small as your platform
+ will consistently measure; large delays are not helpful.
+
+
+
+
+
+ vacuum_cost_page_hit (integer)
+
+
vacuum_cost_page_hit configuration parameter+
+
+
+ The estimated cost for vacuuming a buffer found in the shared
+ buffer cache. It represents the cost to lock the buffer pool,
+ lookup the shared hash table and scan the content of the page.
+ The default value is 1.
+
+
+
+
+
+ vacuum_cost_page_miss (integer)
+
+
vacuum_cost_page_miss configuration parameter+
+
+
+ The estimated cost for vacuuming a buffer that has to be read from
+ disk. This represents the effort to lock the buffer pool,
+ lookup the shared hash table, read the desired block in from
+ the disk and scan its content. The default value is
+ 2.
+
+
+
+
+
+ vacuum_cost_page_dirty (integer)
+
+
vacuum_cost_page_dirty configuration parameter+
+
+
+ The estimated cost charged when vacuum modifies a block that was
+ previously clean. It represents the extra I/O required to
+ flush the dirty block out to disk again. The default value is
+ 20.
+
+
+
+
+
+ vacuum_cost_limit (integer)
+
+
vacuum_cost_limit configuration parameter+
+
+
+ This is the accumulated cost that will cause the vacuuming
+ process to sleep for vacuum_cost_delay. The
+ default is 200.
+
+
+
+
+
+
+ There are certain operations that hold critical locks and should
+ therefore complete as quickly as possible. Cost-based vacuum
+ delays do not occur during such operations. Therefore it is
+ possible that the cost accumulates far higher than the specified
+ limit. To avoid uselessly long delays in such cases, the actual
+ delay is calculated as vacuum_cost_delay *
+ accumulated_balance /
+ vacuum_cost_limit with a maximum of
+ vacuum_cost_delay * 4.
+
+
+
+
+
+
Freezing
+
+ To maintain correctness even after transaction IDs wrap around,
+
PostgreSQL marks rows that are sufficiently
+ old as frozen. These rows are visible to everyone;
+ other transactions do not need to examine their inserting XID to
+ determine visibility. VACUUM is responsible for
+ marking rows as frozen. The following settings control
+ VACUUM's freezing behavior and should be tuned based
+ on the XID consumption rate of the system and data access patterns of the
+ dominant workloads. See for more
+ information on transaction ID wraparound and tuning these parameters.
+
+
+
+
+ vacuum_freeze_table_age (integer)
+
+
vacuum_freeze_table_age configuration parameter+
+
+
+ VACUUM performs an aggressive scan if the table's
+ pg_class.relfrozenxid field has reached
+ the age specified by this setting. An aggressive scan differs from
+ a regular VACUUM in that it visits every page that might
+ contain unfrozen XIDs or MXIDs, not just those that might contain dead
+ tuples. The default is 150 million transactions. Although users can
+ set this value anywhere from zero to two billion, VACUUM
+ will silently limit the effective value to 95% of
+ , so that a
+ periodic manual VACUUM has a chance to run before an
+ anti-wraparound autovacuum is launched for the table. For more
+ information see
+ .
+
+
+
+
+
+ vacuum_freeze_min_age (integer)
+
+
vacuum_freeze_min_age configuration parameter+
+
+
+ Specifies the cutoff age (in transactions) that
+ VACUUM should use to decide whether to
+ trigger freezing of pages that have an older XID.
+ The default is 50 million transactions. Although
+ users can set this value anywhere from zero to one billion,
+ VACUUM will silently limit the effective value to half
+ the value of , so
+ that there is not an unreasonably short time between forced
+ autovacuums. For more information see
+ linkend="vacuum-for-wraparound"/>.
+
+
+
+
+
+ vacuum_failsafe_age (integer)
+
+
vacuum_failsafe_age configuration parameter+
+
+
+ Specifies the maximum age (in transactions) that a table's
+ pg_class.relfrozenxid
+ field can attain before VACUUM takes
+ extraordinary measures to avoid system-wide transaction ID
+ wraparound failure. This is VACUUM's
+ strategy of last resort. The failsafe typically triggers
+ when an autovacuum to prevent transaction ID wraparound has
+ already been running for some time, though it's possible for
+ the failsafe to trigger during any VACUUM.
+
+ When the failsafe is triggered, any cost-based delay that is
+ in effect will no longer be applied, further non-essential
+ maintenance tasks (such as index vacuuming) are bypassed, and any
+ Buffer Access Strategy
+ in use will be disabled resulting in VACUUM being
+ free to make use of all of
+ shared buffers.
+
+ The default is 1.6 billion transactions. Although users can
+ set this value anywhere from zero to 2.1 billion,
+ VACUUM will silently adjust the effective
+ value to no less than 105% of
+ linkend="guc-autovacuum-freeze-max-age"/>.
+
+
+
+
+
+ vacuum_multixact_freeze_table_age (integer)
+
+
vacuum_multixact_freeze_table_age configuration parameter+
+
+
+ VACUUM performs an aggressive scan if the table's
+ pg_class.relminmxid field has reached
+ the age specified by this setting. An aggressive scan differs from
+ a regular VACUUM in that it visits every page that might
+ contain unfrozen XIDs or MXIDs, not just those that might contain dead
+ tuples. The default is 150 million multixacts.
+ Although users can set this value anywhere from zero to two billion,
+ VACUUM will silently limit the effective value to 95% of
+ , so that a
+ periodic manual VACUUM has a chance to run before an
+ anti-wraparound is launched for the table.
+ For more information see .
+
+
+
+
+
+ vacuum_multixact_freeze_min_age (integer)
+
+
vacuum_multixact_freeze_min_age configuration parameter+
+
+
+ Specifies the cutoff age (in multixacts) that VACUUM
+ should use to decide whether to trigger freezing of pages with
+ an older multixact ID. The default is 5 million multixacts.
+ Although users can set this value anywhere from zero to one billion,
+ VACUUM will silently limit the effective value to half
+ the value of ,
+ so that there is not an unreasonably short time between forced
+ autovacuums.
+ For more information see .
+
+
+
+
+
+ vacuum_multixact_failsafe_age (integer)
+
+
vacuum_multixact_failsafe_age configuration parameter+
+
+
+ Specifies the maximum age (in multixacts) that a table's
+ pg_class.relminmxid
+ field can attain before VACUUM takes
+ extraordinary measures to avoid system-wide multixact ID
+ wraparound failure. This is VACUUM's
+ strategy of last resort. The failsafe typically triggers when
+ an autovacuum to prevent transaction ID wraparound has already
+ been running for some time, though it's possible for the
+ failsafe to trigger during any VACUUM.
+
+ When the failsafe is triggered, any cost-based delay that is
+ in effect will no longer be applied, and further non-essential
+ maintenance tasks (such as index vacuuming) are bypassed.
+
+ The default is 1.6 billion multixacts. Although users can set
+ this value anywhere from zero to 2.1 billion,
+ VACUUM will silently adjust the effective
+ value to no less than 105% of
+ linkend="guc-autovacuum-multixact-freeze-max-age"/>.
+
+
+
+
+
+
-
- vacuum_freeze_table_age (integer)
-
-
vacuum_freeze_table_age configuration parameter-
-
-
- VACUUM performs an aggressive scan if the table's
- pg_class.relfrozenxid field has reached
- the age specified by this setting. An aggressive scan differs from
- a regular VACUUM in that it visits every page that might
- contain unfrozen XIDs or MXIDs, not just those that might contain dead
- tuples. The default is 150 million transactions. Although users can
- set this value anywhere from zero to two billion, VACUUM
- will silently limit the effective value to 95% of
- , so that a
- periodic manual VACUUM has a chance to run before an
- anti-wraparound autovacuum is launched for the table. For more
- information see
- .
-
-
-
-
-
- vacuum_freeze_min_age (integer)
-
-
vacuum_freeze_min_age configuration parameter-
-
-
- Specifies the cutoff age (in transactions) that
- VACUUM should use to decide whether to
- trigger freezing of pages that have an older XID.
- The default is 50 million transactions. Although
- users can set this value anywhere from zero to one billion,
- VACUUM will silently limit the effective value to half
- the value of , so
- that there is not an unreasonably short time between forced
- autovacuums. For more information see
- linkend="vacuum-for-wraparound"/>.
-
-
-
-
-
- vacuum_failsafe_age (integer)
-
-
vacuum_failsafe_age configuration parameter-
-
-
- Specifies the maximum age (in transactions) that a table's
- pg_class.relfrozenxid
- field can attain before VACUUM takes
- extraordinary measures to avoid system-wide transaction ID
- wraparound failure. This is VACUUM's
- strategy of last resort. The failsafe typically triggers
- when an autovacuum to prevent transaction ID wraparound has
- already been running for some time, though it's possible for
- the failsafe to trigger during any VACUUM.
-
- When the failsafe is triggered, any cost-based delay that is
- in effect will no longer be applied, further non-essential
- maintenance tasks (such as index vacuuming) are bypassed, and any
- Buffer Access Strategy
- in use will be disabled resulting in VACUUM being
- free to make use of all of
- shared buffers.
-
- The default is 1.6 billion transactions. Although users can
- set this value anywhere from zero to 2.1 billion,
- VACUUM will silently adjust the effective
- value to no less than 105% of
- linkend="guc-autovacuum-freeze-max-age"/>.
-
-
-
-
-
- vacuum_multixact_freeze_table_age (integer)
-
-
vacuum_multixact_freeze_table_age configuration parameter-
-
-
- VACUUM performs an aggressive scan if the table's
- pg_class.relminmxid field has reached
- the age specified by this setting. An aggressive scan differs from
- a regular VACUUM in that it visits every page that might
- contain unfrozen XIDs or MXIDs, not just those that might contain dead
- tuples. The default is 150 million multixacts.
- Although users can set this value anywhere from zero to two billion,
- VACUUM will silently limit the effective value to 95% of
- , so that a
- periodic manual VACUUM has a chance to run before an
- anti-wraparound is launched for the table.
- For more information see .
-
-
-
-
-
- vacuum_multixact_freeze_min_age (integer)
-
-
vacuum_multixact_freeze_min_age configuration parameter-
-
-
- Specifies the cutoff age (in multixacts) that VACUUM
- should use to decide whether to trigger freezing of pages with
- an older multixact ID. The default is 5 million multixacts.
- Although users can set this value anywhere from zero to one billion,
- VACUUM will silently limit the effective value to half
- the value of ,
- so that there is not an unreasonably short time between forced
- autovacuums.
- For more information see .
-
-
-
-
-
- vacuum_multixact_failsafe_age (integer)
-
-
vacuum_multixact_failsafe_age configuration parameter-
-
-
- Specifies the maximum age (in multixacts) that a table's
- pg_class.relminmxid
- field can attain before VACUUM takes
- extraordinary measures to avoid system-wide multixact ID
- wraparound failure. This is VACUUM's
- strategy of last resort. The failsafe typically triggers when
- an autovacuum to prevent transaction ID wraparound has already
- been running for some time, though it's possible for the
- failsafe to trigger during any VACUUM.
-
- When the failsafe is triggered, any cost-based delay that is
- in effect will no longer be applied, and further non-essential
- maintenance tasks (such as index vacuuming) are bypassed.
-
- The default is 1.6 billion multixacts. Although users can set
- this value anywhere from zero to 2.1 billion,
- VACUUM will silently adjust the effective
- value to no less than 105% of
- linkend="guc-autovacuum-multixact-freeze-max-age"/>.
-
-
-
-
bytea_output (enum)
projects / postgresql.git / commitdiff