Developer Options

allow_system_table_mods

Parameter description: Specifies whether the structure of a system catalog and the name of a system schema can be modified.

Parameter type: Boolean.

Unit: none

Value range:

• on: The structure of the system catalog or the name of the system schema can be modified.
• off: The structure of the system catalog or the name of the system schema cannot be modified.

Default value: off

Setting method: This is a POSTMASTER parameter. Set it based on instructions provided in Table 1.

Setting suggestion: You are advised not to modify this parameter.

Risks and impacts of improper settings: If this parameter is enabled, system catalogs may be damaged or even the database cannot be started.

allow_create_sysobject

Parameter description: Specifies whether objects such as functions, stored procedures, synonyms, aggregate functions, and operators can be created or modified in the system schema. The system schema refers to the schema provided by the database after initialization, excluding the public schema. The OID of the system schema is usually smaller than 16384.

Parameter type: Boolean.

Unit: none

Value range:

• on: The initial user and system administrators can create or modify objects such as functions, stored procedures, synonyms, aggregate functions, and operators in the system schema. The SYSADMIN user has permissions to create or replace, alter, grant, and revoke system objects by default. For details about whether other users are allowed to create these objects, see the permission requirements of the corresponding schema.
• off: All users are not allowed to create or modify objects such as functions, stored procedures, synonyms, aggregate functions, and operators in the system schema. The SYSADMIN user does not have permissions to create or replace, alter, grant, and revoke system objects by default.

Default value: on

Setting method: This is a POSTMASTER parameter. Set it based on instructions provided in Table 1.

Setting suggestion: Retain the default value.

Risks and impacts of improper settings: Change the parameter value after fully understanding the parameter meaning and verifying it through testing.

debug_assertions

Parameter description: Specifies whether to enable various assertion checks. To use this parameter, the macro USE_ASSERT_CHECKING must be defined (through the configure option --enable-cassert) during the GaussDB compilation. This parameter can be set at the PDB level.

Parameter type: Boolean.

Unit: none

Value range:

• on: Various assertion checks are enabled.
• off: Various assertion checks are disabled.

Default value: off. In the PDB scenario, if this parameter is not set, the global setting is inherited.

If you compile GaussDB with the assertion check enabled, debug_assertions is set to on by default.

Setting method: This is a USERSET parameter. Set it based on instructions provided in Table 1.

Setting suggestion: This function helps debugging. When an exception or breakdown occurs, enable this function to locate program errors.

Risks and impacts of improper settings: Change the parameter value after fully understanding the parameter meaning and verifying it through testing.

ignore_checksum_failure

Parameter description: Specifies whether to ignore data check errors. This parameter can be set at the PDB level.

Parameter type: Boolean.

Unit: none

Value range:

• on: Data check errors are ignored.
• off: Data check errors are reported.

Default value: off. In the PDB scenario, if this parameter is not set, the global setting is inherited.

Setting method: This is a SUSET parameter. Set it based on instructions provided in Table 1.

Setting suggestion: You are advised not to modify this parameter.

Risks and impacts of improper settings: If this parameter is enabled, the system ignores the failure (but still generates an alarm). Continuing execution may result in breakdown, damaged data being transferred or hidden, failure of data recovery from remote nodes, or other serious problems.

ignore_system_indexes

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

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

Parameter type: Boolean.

Unit: none

Value range:

• on: System indexes are ignored.
• off: System indexes are not ignored.

Default value: off

Setting method: This is a BACKEND parameter. Set it based on instructions provided in Table 1.

Setting suggestion: Retain the default value.

Risks and impacts of improper settings: Change the parameter value after fully understanding the parameter meaning and verifying it through testing.

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.

Parameter type: integer.

Unit: second

Value range: 0 to 2147

Default value: 0, indicating no delay.

Setting method: This is a BACKEND parameter. Set it based on instructions provided in Table 1. For example, if the value is 60 without a unit, post_auth_delay indicates 60s. If the value is 1min, post_auth_delay indicates 1 minute. The unit must be s, min, h, or d if required.

Setting suggestion: 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.

Risks and impacts of improper settings: If this parameter is set to a non-zero value, the database instance 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.

Parameter type: integer.

Unit: second

Value Range: 0 to 60

Default value: 0, indicating no delay.

Setting method: This is a SIGHUP parameter. Set it based on instructions provided in Table 1. For example, if the value is 60 without a unit, pre_auth_delay indicates 60s. If the value is 1min, pre_auth_delay indicates 1 minute. The unit must be s, min, h, or d if required.

Setting suggestion: 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.

Risks and impacts of improper settings: If this parameter is set to a non-zero value, the database instance 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 can be set at the PDB level.

Parameter type: Boolean.

Unit: none

Value range:

• on: The output function is enabled.
• off: The output function is disabled.

Default value: off. In the PDB scenario, if this parameter is not set, the global setting is inherited.

Setting method: This is a USERSET parameter. Set it based on instructions provided in Table 1.

Setting suggestion: Retain the default value.

Risks and impacts of improper settings: Change the parameter value after fully understanding the parameter meaning and verifying it through testing.

trace_recovery_messages

Parameter description: Specifies whether to enable logging of recovery-related debugging output. If it is not enabled, no log is recorded 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 node.

Value type: enumerated type.

Unit: none

Value range: debug5, debug4, debug3, debug2, debug1, and log. For details about the parameters, see Table 1.

Default value: log

• 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 enable logs to be unconditionally recorded into server logs.

trace_sort

Parameter description: Specifies whether to print information about resource usage during sorting operations. This option can be used only when the TRACE_SORT macro is defined during GaussDB compilation. Currently, TRACE_SORT can only be set to the default value and cannot be adjusted. This parameter can be set at the PDB level.

Parameter type: Boolean.

Unit: none

Value range:

• on: Information about resource usage in sorting operations is printed.
• off: Information about resource usage in sorting operations is not printed.

Default value: off. In the PDB scenario, if this parameter is not set, the global setting is inherited.

Setting method: This is a USERSET parameter. Set it based on instructions provided in Table 1.

Setting suggestion: Retain the default value.

Risks and impacts of improper settings: Change the parameter value after fully understanding the parameter meaning and verifying it through testing.

zero_damaged_pages

Parameter description: Specifies whether to terminate the current transaction after a damaged page header that causes GaussDB to report an error is detected. This parameter can be set at the PDB level.

Parameter type: Boolean.

Unit: none

Value range:

• on: The system generates a warning instead of throwing an error, clears the damaged page, and continues 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.
• off: The system does not fill zeros in damaged pages.

Default value: off. In the PDB scenario, if this parameter is not set, the global setting is inherited.

Setting method: This is a SUSET parameter. Set it based on instructions provided in Table 1.

Setting suggestion: In most cases, you are advised not to set it to on if you want to restore data from damaged pages.

Risks and impacts of improper settings: Change the parameter value after fully understanding the parameter meaning and verifying it through testing.

string_hash_compatible

Parameter description: Specifies whether to use the same method to calculate char-type hash values and varchar- or text-type hash values. Based on the setting of this parameter, you can determine whether a redistribution is required when a distribution key is converted from a char-type data distribution into a varchar- or text-type data distribution.

Parameter type: Boolean.

Unit: none

Value range:

• on: The same calculation method is used and a redistribution is not required.
• off: Different calculation methods are used and a redistribution is required.

Calculation methods differ in the length of input strings used for calculating hash values. (For a char-type hash value, spaces following a string are not counted as the length. For a text- or varchar-type hash value, the spaces are counted.) The hash value affects the calculation result of queries. To avoid query errors, do not modify this parameter during database running once it is set.

Default value: off

Setting method: This is a POSTMASTER parameter. Set it based on instructions provided in Table 1.

Setting suggestion: Retain the default value.

Risks and impacts of improper settings: Change the parameter value after fully understanding the parameter meaning and verifying it through testing.

remotetype

Parameter description: Specifies the remote connection type.

Value type: enumerated type.

Unit: none

Value range: application, datanode, and internaltool.

Default value: application

Setting method: This is a BACKEND parameter. Set it based on instructions provided in Table 1.

Setting suggestion: Retain the default value.

Risks and impacts of improper settings: Change the parameter value after fully understanding the parameter meaning and verifying it through testing.

max_user_defined_exception

Parameter description: Specifies the maximum number of exceptions. The default value cannot be changed. This parameter can be set at the PDB level.

Parameter type: integer.

Unit: none

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

Default value: 1000. In the PDB scenario, if this parameter is not set, the global setting is inherited.

Setting method: This is a USERSET parameter. Set it based on instructions provided in Table 1.

Setting suggestion: This parameter can only be viewed.

Risks and impacts of improper settings: none

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 can be set at the PDB level.

Parameter type: Boolean.

Unit: none

Value range:

• on: Optimization for numeric data calculation is enabled.
• off: Optimization for numeric data calculation is disabled.

Default value: on. In the PDB scenario, if this parameter is not set, the global setting is inherited.

Setting method: This is a SUSET parameter. Set it based on instructions provided in Table 1.

Setting suggestion: Retain the default value.

Risks and impacts of improper settings: If this parameter is disabled, the performance of query statements of the numeric type may deteriorate.

enable_fast_vecop

Parameter description: Specifies whether to enable vectorized calculation optimization. The calculation of the Timestamp, int32, int64, and float8 types in the vectorization engine is optimized, the calling cost is reduced, and automatic vectorization calculation is supported. In the multi-tenancy scenario, this parameter can be set at the PDB level.

Parameter type: Boolean.

Unit: none

Value range:

• on: The vectorized operation optimization is enabled.
• off: The vectorized operation optimization is disabled.

Default value: on. In the PDB scenario, if this parameter is not set, the global setting is inherited.

Setting method: This is a USERSET parameter. Set it based on instructions provided in Table 1.

Setting suggestion: Retain the default value.

Risks and impacts of improper settings: If this parameter is disabled, the calculation performance of the Timestamp, int32, int64, and float8 types in the vectorization engine will be affected.

enable_compress_spill

Parameter description: Specifies whether to enable the compression function of writing data to disk. This parameter can be set at the PDB level.

Parameter type: Boolean.

Unit: none

Value range:

• on: The compression function is enabled.
• off: The compression function is disabled.

Default value: on. In the PDB scenario, if this parameter is not set, the global setting is inherited.

Setting method: This is a USERSET parameter. Set it based on instructions provided in Table 1.

Setting suggestion: Retain the default value.

Risks and impacts of improper settings: Change the parameter value after fully understanding the parameter meaning and verifying it through testing.

resource_track_log

Parameter description: Specifies the log level of self-diagnosis. Currently, this parameter takes effect only on multi-column statistics. This parameter can be set at the PDB level.

Value type: enumerated type.

Unit: none

Value range:

• 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. In the PDB scenario, if this parameter is not set, the global setting is inherited.

Setting method: This is a USERSET parameter. Set it based on instructions provided in Table 1.

Setting suggestion: Retain the default value.

Risks and impacts of improper settings: Change the parameter value after fully understanding the parameter meaning and verifying it through testing.

show_acce_estimate_detail

Parameter description: The estimation 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 estimation information is displayed only if the verbose option of the EXPLAIN statement is enabled. (Due to specification changes, the current version no longer supports this feature. Do not use it.) This parameter can be set at the PDB level.

Parameter type: Boolean.

Unit: none

Value range:

• on: The estimation information is displayed in the output of the EXPLAIN statement.

• off: The estimation information is not displayed in the output of the EXPLAIN statement.

Default value: off. In the PDB scenario, if this parameter is not set, the global setting is inherited.

Setting method: This is a USERSET parameter. Set it based on instructions provided in Table 1.

Setting suggestion: Retain the default value.

Risks and impacts of improper settings: Change the parameter value after fully understanding the parameter meaning and verifying it through testing.

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 APIs such as JDBC, ODBC, and libpq.

Parameter type: Boolean.

Unit: none

Value range:

• on: Batch binding and execution are used.
• off: Batch binding and execution are not used.

Default value: on

Setting method: This is a SIGHUP parameter. Set it based on instructions provided in Table 1.

Setting suggestion: Retain the default value.

Risks and impacts of improper settings: Change the parameter value after fully understanding the parameter meaning and verifying it through testing.

batch_error_mode_sp_name

Parameter description: Specifies the name of a savepoint in BatchErrorMode mode.

Parameter type: string.

Unit: none

Value range: a string of 0 to 1023 characters consisting of letters, digits, or underscores (_).

Default value: "BATCH_ERROR_SP"

Setting method: This is a SIGHUP parameter. Set it based on instructions provided in Table 1.

Setting suggestion: Retain the default value.

Risks and impacts of improper settings: Change the parameter value after fully understanding the parameter meaning and verifying it through testing.

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.

Parameter type: string.

Unit: none

Value range: "none" and "all".

• "none": This feature is disabled.
• "all": 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.

In the current version, numa_distribute_mode cannot be set to "all" on the x86 architecture.

Default value: "none"

Setting method: This is a POSTMASTER parameter. Set it based on instructions provided in Table 1.

Setting suggestion: Retain the default value.

Risks and impacts of improper settings: Change the parameter value after fully understanding the parameter meaning and verifying it through testing.

log_pagewriter

Parameter description: Specifies whether to display the page refresh information of threads and details about incremental checkpoints after incremental checkpoints are enabled.

Parameter type: Boolean.

Unit: none

Value range:

• on: Detailed information is displayed.
• off: Detailed information is not displayed.

Default value: off

Setting method: This is a SIGHUP parameter. Set it based on instructions provided in Table 1.

Setting suggestion: You are advised not to set this parameter to on.

Risks and impacts of improper settings: If this parameter is set to on, more information will be displayed, affecting performance.

advance_xlog_file_num

Parameter description: Specifies the number of Xlog files on the standby node that are periodically initialized in advance in the backend.

Parameter type: integer.

Unit: none

Value range: 0 to 1000000. 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

Setting method: This is a POSTMASTER parameter. Set it based on instructions provided in Table 1.

Setting suggestion: This parameter is used to prevent the Xlog file initialization from affecting the performance during transaction commit. However, such a fault may occur only when the system is overloaded. Therefore, you do not need to set this parameter.

Risks and impacts of improper settings: If the value is too large, too much disk space is occupied. As a result, the disk usage is abnormal.

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 can be set at the PDB level.

Parameter type: Boolean.

Unit: none

Value range:

• on: This function is enabled.
• off: This function is disabled.

Default value: off. In the PDB scenario, if this parameter is not set, the global setting is inherited.

Setting method: This is a USERSET parameter. Set it based on instructions provided in Table 1.

Setting suggestion: Retain the default value.

Risks and impacts of improper settings: Change the parameter value after fully understanding the parameter meaning and verifying it through testing.

enable_stream_noblock_memcopy

Parameter description: Specifies whether to enable memory copy optimization for the stream operator. If this parameter is enabled, data in the local stream operator is sent in non-waiting mode, improving the execution efficiency of the local stream operator. In the multi-tenancy scenario, this parameter can be set at the PDB level.

Parameter type: Boolean.

Unit: none

Value range:

• on: Memory copy optimization is enabled for the stream operator.
• off: Memory copy optimization is disabled for the stream operator.

Default value: on. In the PDB scenario, if this parameter is not set, the global setting is inherited.

Setting method: This is a USERSET parameter. Set it based on instructions provided in Table 1.

Setting suggestion: Retain the default value.

Risks and impacts of improper settings: If this parameter is set to off, the execution efficiency of the local stream operator may decrease.

pldebugger_timeout

Parameter description: Specifies the timeout interval for the pldebugger server to wait for a response from the debug end. This parameter can be set at the PDB level.

Parameter type: integer.

Unit: second

Value range: 1 to 86400

Default value: 900 (that is, 15 minutes). In the PDB scenario, if this parameter is not set, the global setting is inherited.

Setting method: This is a USERSET parameter. Set it based on instructions provided in Table 1. For example, if the value is 3600 without a unit, pldebugger_timeout indicates 3600s. If the value is 1h, pldebugger_timeout indicates 1 hour. The unit must be s, min, h, or d if required.

Setting suggestion: Retain the default value.

Risks and impacts of improper settings: Change the parameter value after fully understanding the parameter meaning and verifying it through testing.

plsql_show_all_error

Parameter description: Specifies whether to skip errors and continue compiling PL/SQL objects. For details about the impact, see "Schema > DBE_PLDEVELOPER" in Developer Guide. This parameter can be set at the PDB level.

Parameter type: Boolean.

Unit: none

Value range:

• on: When PL/SQL objects are compiled, errors can be skipped and the compilation continues.
• off: When PL/SQL objects are compiled, errors cannot be skipped and the compilation cannot continue.

Default value: off. In the PDB scenario, if this parameter is not set, the global setting is inherited.

Setting method: This is a USERSET parameter. Set it based on instructions provided in Table 1.

Setting suggestion: Retain the default value.

Risks and impacts of improper settings: Change the parameter value after fully understanding the parameter meaning and verifying it through testing.

ustore_attr

Parameter description: This parameter is used to control the information statistics of Ustore tables, rollback type, UB-tree index type, and data verification during the running of key modules (including data, indexes, rollback segments, and replay). This parameter helps R&D engineers locate faults. This parameter can be set at the PDB level.

Parameter type: string.

Unit: none

Value range: This parameter is set in key-value mode. The mapping between keys and values is as follows: If multiple key-value pairs are used, use semicolons (;) to separate them. For example, ustore_attr='ustore_verify_level=FAST;ustore_verify_module=UPAGE:UBTREE:UNDO:REDO'.

• ustore_verify_level: verification level.

  Value range: a string of case-insensitive characters. For details, see the following table.

  Table 1 Parameter value meaning of ustore_verify_level

  Parameter Value	Description
  NONE	NONE indicates that the verification function is disabled. You are advised to enable this function to test performance.
  FAST	Indicates fast verification. Few content is to be verified and the impact on performance is minimized. The value is NORMAL for compatibility with earlier versions.
  COMPLETE	Indicates complete verification. The verification content is the largest and the performance is greatly affected. The value is SLOW for compatibility with earlier versions.

  Default value: FAST

• ustore_verify_module: module that controls verification.

  Value range: The value can be one or more of UPAGE, UBTREE, UNDO, REDO, and ROACH, or it can be ALL or NULL (case-insensitive). When multiple values are used, separate them with colons (:). For example, ustore_verify_module=UPAGE:UBTREE:UNDO:REDO.

  When the ROACH module is enabled, the value of the ustore_verify_level parameter is ignored during the ROACH backup. By default, the level of verification is the highest and the performance is greatly affected. Therefore, exercise caution when using this parameter.

  Table 2 Parameter value meaning of ustore_verify_module

  Parameter Value	Description
  UPAGE	Indicates that data page verification is enabled.
  UBTREE	Indicates that UB-tree index verification is enabled.
  UNDO	Indicates that rollback segment data verification is enabled.
  REDO	Indicates that data page verification for the REDO process is enabled.
  ROACH	This parameter is discarded. The verification has been removed from the underlying logic. ustore_verify_module can be set to roach but it does not take effect.
  ALL	Indicates that data verification is enabled for the UPAGE, UBTREE, UNDO, REDO, and ROACH modules.
  NULL	Indicates that data verification for the UPAGE, UBTREE, UNDO, REDO, and ROACH modules is disabled.

  Default value: UPAGE:UBTREE:UNDO

• index_trace_level: specifies whether to enable index tracing and controls the printing level. After this function is enabled, information about index tuples that meet the conditions is printed based on the printing level during index scan.

  Value range: The values are described in the following table.

  Default value: NO

  Table 3 Parameter value meaning of index_trace_level

  Parameter Value	Description
  NO	No additional information is printed.
  NORMAL	Information about visible index tuples is printed, including: ID and offset of the index page where the current index tuple is located Current tuple status TID and partOid corresponding to the current tuple xmin and xmax information corresponding to the current tuple Current tuple content (if enable_log_tuple is set to on).
  VISIBILITY	On the basis of NORMAL, the information about the index tuples that do not pass the visibility check is printed and whether the index tuples are visible is marked.
  SHOWHIKEY	On the basis of VISIBILITY, the system tries to print the information about the HIKEY tuple on the page.
  ALL	Information about all tuples on the scanned index page is printed.

• enable_log_tuple: specifies whether to print the contents of related tuples when printing log-level prompts for troubleshooting and locating.

  Value range: on or off (case-insensitive)

  Default value: off

  Remarks: This parameter has been discarded.

• enable_ustore_sync_rollback: specifies whether to enable synchronous rollback for Ustore tables.

  Value range: Boolean

  Default value: true

• enable_ustore_async_rollback: specifies whether to enable asynchronous rollback for Ustore tables.

  Value range: Boolean

  Default value: true

• enable_ustore_page_rollback: specifies whether to enable page rollback for Ustore tables.

  Value range: Boolean

  Default value: true

• enable_ustore_partial_seqscan: specifies whether to enable partial scan for Ustore tables.

  Value range: Boolean

  Default value: false

• enable_candidate_buf_usage_count: specifies whether to enable buffer usage statistics.

  Value range: Boolean

  Default value: false

• ustats_tracker_naptime: specifies the interval for collecting statistics on Ustore tables.

  Value range: 1 to 1073741

  Default value: 20, in seconds.

• umax_search_length_for_prune: specifies the maximum search depth of the prune operation on the Ustore table.

  Value range: 1 to 1073741

  Default value: 10

When setting ustore_attr, do not leave spaces or other characters before and after the equal sign (=) between key and value, for example, ustore_attr='ustore_verify_level = FAST;. Otherwise, the parameter is invalid during kernel code verification and the parameter setting fails.

Default value: "ustore_verify_level=FAST;ustore_verify_module=UPAGE:UBTREE:UNDO". In the PDB scenario, if this parameter is not set, the global setting is inherited.

Setting method: This is a USERSET parameter. Set it based on instructions provided in Table 1.

Setting suggestion: Exercise caution when setting the ustore_attr parameter. You are advised to modify it with the assistance of engineers.

Risks and impacts of improper settings: Change the parameter value after fully understanding the parameter meaning and verifying it through testing.

index_txntype

Parameter description: Specifies whether the index type of UB-tree is PCR or RCR. PCR supports flashback query based on indexes, but RCR does not. An empty character string is equivalent to RCR in most scenarios. In the reindex scenario, if the value is an empty character string, the index type is not changed. If the value is "RCR", the index type is forcibly rebuilt. This parameter can be set at the PDB level.

Parameter type: string.

Unit: none

Value range: "", "PCR", and "RCR".

Default value: "". In the PDB scenario, if this parameter is not set, the global setting is inherited.

Setting method: This is a USERSET parameter. Set it based on instructions provided in Table 1.

Setting suggestion: If the PCR index is required, set this parameter to "PCR". Otherwise, you are advised not to change the value.

Risks and impacts of improper settings: Change the parameter value after fully understanding the parameter meaning and verifying it through testing.

enable_segment_remain_cleanup

Parameter description: Specifies which the residual segment-page cleanup feature is to be enabled.

Parameter type: Boolean.

Unit: none

Value range:

• on: indicates that the old type of residual segment-page cleanup is enabled.
  • Query APIs: gs_stat_remain_segment_info() and gs_local_stat_remain_segment_info().
  • Cleanup APIs: gs_free_remain_segment() and gs_local_free_remain_segment().
• off: indicates that the new type of residual segment-page cleanup is enabled.
  • Query APIs: gs_seg_spc_remain_segments() and gs_seg_spc_remain_extents().
  • Cleanup APIs: gs_seg_free_spc_remain_segment() and gs_seg_free_spc_remain_extent().

Default value: off

Setting method: This is a POSTMASTER parameter. Set it based on instructions provided in Table 1.

Setting suggestion: Retain the default value.

Risks and impacts of improper settings: Do not switch the clearing mode randomly. Otherwise, residual segment-page data may fail to be cleared or other exceptions may occur.

convert_illegal_char_mode

Parameter description: Specifies the placeholders of invalid characters that can be displayed on the client when the enable_convert_illegal_char parameter is enabled. In the multi-tenancy scenario, this parameter can be set at the PDB level.

Parameter type: string.

Unit: none

Value range: 95 characters whose decimal codes range from 32 to 126 in the ASCII coding table.

Default value: "?". In the PDB scenario, if this parameter is not set, the global setting is inherited.

Setting method: This is a USERSET parameter. Set it based on instructions provided in Table 1.

Setting suggestion: Retain the default value.

Risks and impacts of improper settings: Change the parameter value after fully understanding the parameter meaning and verifying it through testing.

default_segment

Parameter description: Specifies whether to create a segment-page table by default. In the multi-tenancy scenario, this parameter can be set at the PDB level.

Parameter type: Boolean.

Unit: none

Value range:

• on: A segment-page table is created by default when the segment column is not specified.
• off: A page table is created by default when the segment column is not specified.

Default value: off. In the PDB scenario, if this parameter is not set, the global setting is inherited.

Setting method: This is a SUSET parameter. Set it based on instructions provided in Table 1.

Setting suggestion: Retain the default value.

Risks and impacts of improper settings: Change the parameter value after fully understanding the parameter meaning and verifying it through testing.

• If --undostoragetype is set to 'segpage' during database initialization, the data of Ustore is forcibly stored in segment-page mode, but Astore is not affected.
• If --undostoragetype is set to 'page' or is not set during database initialization, the data of Ustore is forcibly stored in page mode, but Astore is not affected.