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allow_system_table_mods

Parameter description: Specifies whether the structures of system tables can be modified.

This parameter is a POSTMASTER parameter. Set it based on instructions provided in Table 1 GUC parameters.

It is not recommended to modify the default value of this parameter. If it is set to on, the system tables may be damaged and the database may not start.

Value range: Boolean

  • on indicates that the structures of system tables can be modified.
  • off indicates that the structures of system tables cannot be modified.

Default value:off

debug_assertions

Parameter description: Specifies whether to enable various assertion checks. This parameter assists in debugging. If you are experiencing strange problems or crashes, set this parameter to on to identify programming defects. To use this parameter, the macro USE_ASSERT_CHECKING must be defined (through the configure option –enable-cassert) during the MogDB compilation.

This parameter is a USERSET parameter. Set it based on instructions provided in Table 1 GUC parameters.

Value range: Boolean

  • on indicates that various assertion checks are enabled.
  • off indicates that various assertion checks are disabled.

img NOTE: This parameter is set to on by default if MogDB is compiled with various assertion checks enabled.

Default value:off

ignore_checksum_failure

Parameter description: Specifies whether to ignore check failures (but still generates an alarm) and continues reading data. Continuing reading data may result in breakdown, damaged data being transferred or hidden, failure of data recovery from remote nodes, or other serious problems. You are not advised to modify the settings.

This parameter is a SUSET parameter. Set it based on instructions provided in Table 1 GUC parameters.

Value range: Boolean

  • on indicates that data check errors are ignored.
  • off indicates that data check errors are reported.

Default value:off

ignore_system_indexes

Parameter description: Specifies whether to ignore system indexes when reading system tables (but still update the indexes when modifying the tables).

This parameter is a BACKEND parameter. Set it based on instructions provided in Table 1 GUC parameters.

img NOTICE: This parameter is useful for recovering data from tables whose system indexes are damaged.

Value range: Boolean

  • on indicates that system indexes are ignored.
  • off indicates that system indexes are not ignored.

Default value: off

post_auth_delay

Parameter description: Specifies the delay in the connection to the server after a successful authentication. Developers can attach a debugger to the server startup process.

This parameter is a BACKEND parameter. Set it based on instructions provided in Table 1 GUC parameters.

Value range: an integer ranging from 0 to 2147. The unit is s.

Default value: 0

img NOTE: This parameter is used only for commissioning and fault locating. To prevent impact on service running, ensure that the default value 0 is used in the production environment. If this parameter is set to a value other than 0, the cluster status may be abnormal due to a long authentication delay.

pre_auth_delay

Parameter description: Specifies the period of delaying authentication after the connection to the server is started. Developers can attach a debugger to the authentication procedure.

This parameter is a SIGHUP parameter. Set it based on instructions provided in Table 1 GUC parameters.

Value range: an integer ranging from 0 to 60. The unit is s.

Default value: 0

img NOTE: This parameter is used only for commissioning and fault locating. To prevent impact on service running, ensure that the default value 0 is used in the production environment. If this parameter is set to a value other than 0, the cluster status may be abnormal due to a long authentication delay.

trace_notify

Parameter description: Specifies whether to enable the function of generating debugging output for the LISTEN and NOTIFY commands. The level of client_min_messages or log_min_messages must be debug1 or lower so that debugging output can be recorded in the client or server logs, respectively.

This parameter is a USERSET parameter. Set it based on instructions provided in Table 1 GUC parameters.

Value range: Boolean

  • on indicates that the function is enabled.
  • off indicates that the function is disabled.

Default value: off

trace_recovery_messages

Parameter description: Specifies whether to enable logging of recovery-related debugging output. This parameter allows users to overwrite the normal setting of log_min_messages, but only for specific messages. This is intended for the use in debugging the standby server.

This parameter is a SIGHUP parameter. Set it based on instructions provided in Table 1 GUC parameters.

Value range: enumerated values. Valid values include debug5, debug4, debug3, debug2, debug1, and log. For details about the parameter values, see log_min_messages.

Default value: log

img NOTE:

  • log indicates that recovery-related debugging information will not be logged.
  • Except the default value log, each of the other values indicates that recovery-related debugging information at the specified level will also be logged. Common settings of log_min_messages enables logs to be unconditionally recorded into server logs.

trace_sort

Parameter description: Specifies whether to print information about resource usage during sorting operations. This parameter is available only when the macro TRACE_SORT is defined during the GaussDB Kernel compilation. However, TRACE_SORT is currently defined by default.

This parameter is a USERSET parameter. Set it based on instructions provided in Table 1 GUC parameters.

Value range: Boolean

  • on indicates that the function is enabled.
  • off indicates that the function is disabled.

Default value: off

zero_damaged_pages

Parameter description: Specifies whether to detect a damaged page header that causes GaussDB Kernel to report an error, aborting the current transaction.

This parameter is a SUSET parameter. Set it based on instructions provided in Table 1 GUC parameters.

Value range: Boolean

Setting this parameter to on causes the system to report a warning, zero out the damaged page, and continue processing. This behavior will destroy data, including all the rows on the damaged page. However, it allows you to bypass the error and retrieve rows from any undamaged pages that may be present in the table. Therefore, it is useful for restoring data if corruption has occurred due to a hardware or software error. In most cases, you are advised not to set this parameter to on if you want to restore data from damaged pages.

Default value: off

remotetype

Parameter description: Specifies the remote connection type.

This parameter cannot be changed.

Value range: enumerated values. Valid values are application, datanode, and internaltool.

Default value: application

max_user_defined_exception

Parameter description: Specifies the maximum number of exceptions. The default value cannot be changed.

This parameter is a USERSET parameter. Set it based on instructions provided in Table 1 GUC parameters.

Value range: an integer. Currently, only the fixed value 1000 is supported.

Default value: 1000

enable_fast_numeric

Parameter description: Specifies whether to enable optimization for numeric data calculation. Calculation of numeric data is time-consuming. Numeric data is converted into int64- or int128-type data to improve numeric data calculation performance.

This parameter is a SUSET parameter. Set it based on instructions provided in Table 1 GUC parameters.

Value range: Boolean

  • on or true indicates that optimization for numeric data calculation is enabled.
  • off or false indicates that optimization for numeric data calculation is disabled.

Default value: on

enable_compress_spill

Parameter description: Specifies whether to enable the compression function of writing data to disk.

This parameter is a USERSET parameter. Set it based on instructions provided in Table 1 GUC parameters.

Value range: Boolean

  • on or true indicates that optimization for writing data to disk is enabled.
  • off or false indicates that optimization for writing data to a disk is disabled.

Default value: on

resource_track_log

Parameter description: Specifies the log level of self-diagnosis. Currently, this parameter takes effect only in multi-column statistics.

This parameter is a USERSET parameter. Set it based on instructions provided in Table 1 GUC parameters.

Value range: a string

  • summary: Brief diagnosis information is displayed.
  • detail: Detailed diagnosis information is displayed.

Currently, the two parameter values differ only when there is an alarm about multi-column statistics not collected. If the parameter is set to summary, such an alarm will not be displayed. If it is set to detail, such an alarm will be displayed.

Default value: summary

show_acce_estimate_detail

Parameter description: The evaluation information is generally used by O&M personnel during maintenance, and it may affect the output display of the EXPLAIN statement. Therefore, this parameter is disabled by default. The evaluation information is displayed only if the verbose option of the EXPLAIN statement is enabled.

This parameter is a USERSET parameter. Set it based on instructions provided in Table 1 GUC parameters.

Value range: Boolean

  • on indicates that the evaluation information is displayed in the output of the EXPLAIN statement.
  • off indicates that the evaluation information is not displayed in the output of the EXPLAIN statement.

Default value: off

img NOTE: The current version does not support database acceleration. Therefore, this parameter does not take effect after being set.

support_batch_bind

Parameter description: Specifies whether to batch bind and execute PBE statements through interfaces such as JDBC, ODBC, and libpq.

This parameter is a SIGHUP parameter. Set it based on instructions provided in Table 1 GUC parameters.

Value range: Boolean

  • on indicates that batch binding and execution are used.
  • off indicates that batch binding and execution are not used.

Default value: on

numa_distribute_mode

Parameter description: Specifies the distribution of some shared data and threads among NUMA nodes. This parameter is used to optimize the performance of large-scale ARM servers with multiple NUMA nodes. Generally, you do not need to set this parameter.

This parameter is a POSTMASTER parameter. Set it based on instructions provided in Table 1 GUC parameters.

Value range: a string. The valid values are none and all.

  • none indicates that this function is disabled.
  • all indicates that some shared data and threads are distributed to different NUMA nodes to reduce the number of remote access times and improve performance. Currently, this function applies only to ARM servers with multiple NUMA nodes. All NUMA nodes must be available for database processes. You cannot select only some NUMA nodes.

Default value: none

log_pagewriter

Parameter description: Specifies whether to display the page refresh information of a thread and details about an incremental check point after the incremental check point is enabled. You are not advised to set this parameter to true because a large amount of information will be generated.

This parameter is a SIGHUP parameter. Set it based on instructions provided in Table 1 GUC parameters.

Value range: Boolean

Default value: on

advance_xlog_file_num

Parameter description: Specifies the number of Xlog files that are periodically initialized in advance in the background. This parameter is used to prevent the Xlog file initialization from affecting the performance during transaction submission. However, such a fault may occur only when the system is overloaded. Therefore, you do not need to set this parameter.

This parameter is a POSTMASTER parameter. Set it based on instructions provided in Table 1 GUC parameters.

Value range: an integer ranging from 0 to 100. The value 0 indicates that initialization is not performed in advance. For example, the value 10 indicates that the background thread periodically initializes 10 Xlog files in advance based on the write location of the current xlog.

Default value: 0

enable_beta_opfusion

Parameter description: Specifies whether to accelerate the execution of SQL statements, such as aggregate functions and sorting in TPC-C when enable_opfusion is set to on.

This parameter is a USERSET parameter. Set it based on instructions provided in Table 1 GUC parameters.

Value range: Boolean

  • on indicates that the functions are enabled.
  • off indicates that the function are disabled.

Default value: off