Miscellaneous Parameters

enable_default_ustore_table

Parameter description: Specifies whether to enable the Ustore storage engine by default. If this parameter is set to on, all created tables are Ustore tables.

This is a USERSET parameter. Set it based on instructions provided in Table 1. Note that the track_counts and track_activities parameters must be enabled when the Ustore table is used. Otherwise, space expansion may occur.

Value range: [off, on]

Default value: off

enable_ustore

Parameter description: Specifies whether to enable the Ustore storage engine. If this parameter is set to on, Ustore tables can be created. Note that the track_counts and track_activities parameters must be enabled when the Ustore table is used. Otherwise, space expansion may occur.

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

Value range: [off, on]

Default value: on

reserve_space_for_nullable_atts

Parameter description: Specifies whether to reserve space for the nullable attribute of an Ustore table. If this parameter is set to on, space is reserved for the nullable attribute of the Ustore table by default.

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

Value range: [off, on]

Default value: on

server_version

Parameter description: Specifies the server version number (string).

This parameter is a fixed INTERNAL parameter and cannot be modified. This parameter is inherited from the PostgreSQL kernel, indicating that the current database kernel is compatible with PostgreSQL's server_version. This parameter is reserved to ensure the ecosystem compatibility of the northbound external tool APIs (which will be queried when the tool is connected). This parameter is not recommended. You can use the opengauss_version() function to obtain the kernel version.

Value range: a string.

Default value: 9.2.4

server_version_num

Parameter description: Specifies the server version number (integer).

This parameter is a fixed INTERNAL parameter and cannot be modified. This parameter is inherited from the PostgreSQL kernel, indicating that the current database kernel is compatible with PostgreSQL's server_version_num. This parameter is reserved to ensure the ecosystem compatibility of the northbound external tool APIs (which will be queried when the tool is connected).

Value range: an integer

Default value: 90204

block_size

Parameter description: Specifies the block size of the current database.

This parameter is a fixed INTERNAL parameter and cannot be modified. This parameter is inherited from the PostgreSQL kernel, indicating that the current database kernel is compatible with PostgreSQL's server_version_num. This parameter is reserved to ensure the ecosystem compatibility of the northbound external tool APIs.

Default value: 8192

segment_size

Parameter description: Specifies the segment file size of the current database.

This is a fixed INTERNAL parameter. It can be viewed but cannot be modified.

Default value: 1 GB

max_index_keys

Parameter description: Specifies the maximum number of index keys supported by the current database.

This is a fixed INTERNAL parameter. It can be viewed but cannot be modified.

Default value: 32

integer_datetimes

Parameter description: Specifies whether the date and time are in the 64-bit integer format.

This is a fixed INTERNAL parameter. It can be viewed but cannot be modified.

Value range: Boolean

• on indicates that the 64-bit integer format is used.
• off indicates that the 64-bit integer format is not used.

Default value: on

enable_cluster_resize

Parameter description: If an SQL statement involves tables belonging to different groups, you can enable this parameter to push the execution plan of the statement to improve performance.

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

Value range: Boolean

• on indicates that the execution plan of the statement can be pushed.
• off indicates that the execution plan of the statement cannot be pushed.

Default value: off

This parameter is used for internal O&M. Do not set it to on unless absolutely necessary.

lc_collate

Parameter description: Specifies the locale in which sorting of textual data is done.

This is a fixed INTERNAL parameter. It can be viewed but cannot be modified.

Default value: Determined by the configuration set during the cluster installation and deployment.

lc_ctype

Parameter description: Specifies the locale that determines character classifications. For example, it specifies what a letter and its upper-case equivalent are.

This is a fixed INTERNAL parameter. It can be viewed but cannot be modified.

Default value: Determined by the configuration set during the cluster installation and deployment.

max_identifier_length

Parameter description: Specifies the maximum identifier length.

This is a fixed INTERNAL parameter. It can be viewed but cannot be modified.

Value range: an integer

Default value: 63

server_encoding

Parameter description: Specifies the database encoding (character set).

This is a fixed INTERNAL parameter. It can be viewed but cannot be modified.

Default value: Determined when the database is created.

enable_upgrade_merge_lock_mode

Parameter description: If this parameter is set to on, the delta merge operation internally increases the lock level, and errors can be prevented when update and delete operations are performed at the same time.

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

Value range: Boolean

• If this parameter is set to on, the delta merge operation internally increases the lock level. In this way, when the DELTAMERGE operation is concurrently performed with the UPDATE or DELETE operation, one operation can be performed only after the previous one is complete.
• If this parameter is set to off and the DELTAMERGE operation is concurrently performed with the UPDATE or DELETE operation to the data in a row in the delta table of the table, errors will be reported during the later operation, and the operation will stop.

Default value: off

transparent_encrypted_string

Parameter description: This parameter is discarded. It stores a sample string that is transparently encrypted. After the fixed string TRANS_ENCRYPT_SAMPLE_STRING is encrypted using a database encryption key, ciphertext is obtained to check whether the DEK obtained during second startup is correct. If the DEK is incorrect, CNs and DNs reject the startup. This parameter is a POSTMASTER parameter. Set it based on instructions provided in Table 1.

Value range: a string. An empty string indicates that the entire cluster is encrypted.

Default value: empty.

Do not set this parameter manually. Otherwise, the cluster may become faulty.

transparent_encrypt_kms_url

Parameter description: This parameter is discarded. It stores the address for obtaining the database key that is transparently encrypted. The content must contain only the characters specified in RFC3986, and the maximum length is 2047 bytes. The format is kms://Protocol@KMS host name 1;KMS host name 2:KMS port number/kms, for example, kms://https@linux175:29800/.

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

Value range: a string.

Default value: empty.

transparent_encrypt_kms_region

Parameter description: This parameter is discarded. It stores the deployment region of the entire cluster. The content must contain only the characters specified in RFC3986, and the maximum length is 2047 bytes.

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

Value range: a string.

Default value: empty.

datanode_heartbeat_interval

Parameter description: Specifies the interval at which heartbeat messages are sent between heartbeat threads. You are advised to set this parameter to a value no more than wal_receiver_timeout/2.

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

Value range: an integer ranging from 1000 to 60000. The unit is ms.

Default value: 1s

dfs_partition_directory_length

Parameter description: Specifies the maximum directory name length for the partition directory of a table partitioned by VALUE in the HDFS.

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

Value range: 92 to 7999

Default value: 512

max_concurrent_autonomous_transactions

Parameter description: Specifies the maximum number of autonomous transaction connections, that is, the maximum number of concurrent autonomous transactions executed at the same time. If this parameter is set to 0, autonomous transactions cannot be executed.

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

Value range: 0–10000. The theoretical maximum value is 10000, and the actual maximum value is a dynamic value. The calculation formula is 262143 – job_queue_processes – autovacuum_max_workers – max_inner_tool_connections – max_connections – AUXILIARY_BACKENDS – AV_LAUNCHER_PROCS. The values of job_queue_processes, autovacuum_max_workers, max_inner_tool_connections, and max_connections depend on the settings of the corresponding GUC parameters. AUXILIARY_BACKENDS indicates the number of reserved auxiliary threads, which is fixed to 20. AV_LAUNCHER_PROCS indicates the number of reserved launcher threads for autovacuum, which is fixed to 2.

Default value:

Independent deployment: 80 (60-core CPU/480 GB memory); 40 (32-core CPU/256 GB memory); 20 (16-core CPU/128 GB memory); 10 (8-core CPU/64 GB memory, 4-core CPU/32 GB memory, 4-core CPU/16 GB memory)

Suggestion: Set this parameter based on actual service requirements and hardware configurations. It is recommended that this parameter be set to a value less than or equal to 1/10 of max_connections. If you only increase the value of this parameter but do not adjust the memory parameters in the same proportion, the memory may be insufficient and the error message "memory is temporarily unavailable" is displayed when the service load is heavy.

If the value range of this parameter is changed during the upgrade and the value is changed before the commit operation, you need to change the value range to the value allowed before the upgrade if you roll back the upgrade. Otherwise, the database may fail to be started.

mot_config_file

This parameter is unavailable in a distributed system.

enable_gpi_auto_update

Parameter description: Determines whether global indexes are updated by default in partition DDL commands.

This parameter is a USERSET parameter. Set it based on instructions provided in Table 1. This parameter must be set to the same value on CNs and DNs. Otherwise, the global index function may be abnormal.

Value range: Boolean

• The value on indicates that global indexes are updated regardless of whether the partition DDL commands contain the UPDATE GLOBAL INDEX clause.
• The value off indicates that global indexes are not updated unless the partition DDL commands contain the UPDATE GLOBAL INDEX clause.

Default value: off

change_cluster_mode

Parameter description: Specifies whether the cluster is in the mode switchover process. Mode switchover refers to: A cluster with one primary and two standby nodes is switched to a cluster with one primary node, one standby node, and one log; a cluster with one primary node, one standby node, and one log is switched to a cluster with one primary and two standby nodes; standby DNs and log DNs in a cluster with one primary node, one standby node, and one log are switched to each other.

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

Value range: an integer ranging from 0 to 2147483647

• The value 0 indicates that the cluster mode is not being switched.
• The value 1 indicates that the cluster mode is being switched.
• Other values are meaningless and have the same effect as the value 0.

Default value: 0

This parameter specifies whether the read function of the standby node in a distributed system is available. If this parameter is set to 1, the read function of the standby node in a distributed system cannot be used. Exercise caution when setting this parameter.