Primary Server

synchronous_standby_names

Parameter description: Specifies a comma-separated list of names of potential standby servers that support synchronous replication.

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

NOTICE:

The current synchronous standby server is on the top of the list. If the current synchronous standby server is disconnected, it will be replaced immediately with the next-highest-priority standby server. Name of the next-highest-priority standby server is added to the list.

The standby node name can be specified by setting the environment variable PGAPPNAME.

Value range: a string. If this parameter is set to *****, the name of any standby server that provides synchronous replication is matched. The value can be configured in the following format:

ANY num_sync (standby_name [, …]) [, ANY num_sync (standby_name [, …])]
[FIRST] num_sync (standby_name [, …])
standby_name [, …]
NOTE:
- In the preceding command, num_sync indicates the number of standby nodes that need to wait for responses from the transaction, standby_name indicates the name of the standby node, and FIRST and ANY specify the policies for selecting standby nodes for synchronous replication from the listed servers.
- ANY N (dn_instanceId1, dn_instanceId2,…) indicates that any N host names in the brackets are selected as the name list of standby nodes for synchronous replication. For example, ANY 1(dn_instanceId1, dn_instanceId2) indicates that any one of dn_instanceId1 and dn_instanceId2 is used as the standby node for synchronous replication.
- FIRST N (dn_instanceId1, dn_instanceId2, …) indicates that the first N primary node names in the brackets are selected as the standby node name list for synchronous replication based on the priority. For example, FIRST 1 (dn_instanceId1, dn_instanceId2) indicates that dn_instanceId1 is selected as the standby node for synchronous replication.
- The meanings of dn_instanceId1, dn_instanceId2, … are the same as those of FIRST 1 (dn_instanceId1, dn_instanceId2, …).

If you use the gs_guc tool to set this parameter, perform the following operations:

gs_guc reload -Z datanode -N @NODE_NAME@ -D @DN_PATH@ -c "synchronous_standby_names='ANY NODE 1(dn_instanceId1, dn_instanceId2)'";

gs_guc reload -Z datanode -N @NODE_NAME@ -D @DN_PATH@ -c "synchronous_standby_names='ANY 1(AZ1, AZ2)'";

Default value: *****

most_available_sync

Parameter description: Specifies whether to block the primary server when the primary-standby synchronization fails.

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

Value range: Boolean

on indicates that the primary server is not blocked when the synchronization fails.
off indicates that the primary server is blocked when the synchronization fails.

Default value: off

keep_sync_window

Parameter description: Specifies the delay for entering the maximum availability mode.

If most_available_sync is set to on, when synchronous standby nodes are faulty in primary/standby scenarios and the number of configured synchronous standby nodes is insufficient (for details, see the meaning of synchonous_standby_name), setting keep_sync_window will retain the maximum protection mode within the time window specified by keep_sync_window. That is, committing transactions on the primary node is blocked, delay the primary node to enter the maximum availability mode.
If synchronous standby nodes recover from faults and the number of synchronous standby nodes meets the configuration requirements, transactions are not blocked.
You are advised to set keep_sync_window to 5s. This prevents the monitoring system from incorrectly reporting network instability.

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 INT_MAX. The unit is second.

The value 0 indicates that the keep_sync_window is not set, that is, the maximum availability mode is entered directly.
Other values indicate the size of the timeout window.

Default value: 0

NOTE: Setting this parameter may affect the RPO. If the primary node is faulty within the configured timeout window, the data generated from the time when the primary node is blocked to the time when the primary node is faulty may be lost.

enable_stream_replication

Parameter description: Specifies whether data and logs are synchronized between primary and standby servers, and between primary and secondary servers.

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

NOTICE:

This parameter is used for performance testing in scenarios where data synchronization to standby server is enabled and where it is disabled. If this parameter is set to off, tests on abnormal scenarios, such as switchover and faults, cannot be performed to prevent inconsistency between the primary, standby, and secondary servers.

This parameter is a restricted parameter, and you are advised not to set it to off in normal service scenarios.

Currently, primary/standby/secondary deployment is not supported by default.

Value range: Boolean

on indicates that data and log synchronization is enabled.
off indicates that data and log synchronization is disabled.

Default value: on

enable_mix_replication

Parameter description: Specifies how WAL files and data are replicated between primary and standby servers, and between primary and secondary servers.

This parameter is an INTERNAL parameter. Its default value is off and cannot be modified.

NOTICE:

This parameter cannot be modified in normal service scenarios. That is, the WAL file and data page mixed replication mode is disabled.

Currently, primary/standby/secondary deployment is not supported by default.

Value range: Boolean

on indicates that the WAL file and data page mixed replication mode is enabled.
off indicates that the WAL file and data page mixed replication mode is disabled.

Default value: off

vacuum_defer_cleanup_age

Parameter description: Specifies the number of transactions by which VACUUM will defer the cleanup of invalid row-store table records, so that VACUUM and VACUUM FULL do not clean up deleted tuples immediately.

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 1000000. 0 means no delay.

Default value: 0

data_replicate_buffer_size

Parameter description: Specifies the amount of memory used by queues when the sender sends data pages to the receiver. The value of this parameter affects the buffer size used during the replication from the primary server to the standby server.

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

Value range: an integer ranging from 4096 to 1072693248. The unit is kB.

Default value: 16MB (16448 kB)

walsender_max_send_size

Parameter description: Specifies the size of the WAL or Sender buffers on the primary server.

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

Value range: an integer ranging from 8 to INT_MAX. The unit is kB.

Default value: 8MB (8192 kB)

enable_data_replicate

Parameter description: Specifies how data is synchronized between primary and standby servers when the data is imported to a row-store table.

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

Value range: Boolean

on indicates that the primary and standby servers synchronize data using data pages when the data is imported to a row-store table. When replication_type is set to 1, this parameter cannot be set to on. If this parameter is set to on using the GUC tool, its value will be forcibly changed to off.
off indicates that the primary and standby servers synchronize data using Xlogs when the data is imported to a row-store table.

Default value: off

ha_module_debug

Parameter description: Specifies the replication status log of a specific data block during data replication.

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

Value range: Boolean

on indicates that the status of each data block is recorded in logs during data replication.
off indicates that the status of each data block is not recorded in logs during data replication.

Default value: off

enable_incremental_catchup

Parameter description: Specifies the data catchup mode between the primary and standby nodes. Currently, primary/standby/secondary deployment is not supported by default.

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

Value range: Boolean

on indicates that the standby server uses the incremental catchup mode. That is, the standby server scans local data files on the standby server to obtain the list of differential data files between the primary and standby servers and then performs catchup between the primary and standby servers.
off indicates that the standby server uses the full catchup mode. That is, the standby server scans all local data files on the primary server to obtain the list of differential data files between the primary and standby servers and performs catchup between the primary and standby servers.

Default value: on

wait_dummy_time

Parameter description: Specifies the maximum duration for the primary server to wait for the standby and secondary servers to start and send the scanning lists when incremental data catchup is enabled in MogDB.

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

Value range: an integer ranging from 1 to INT_MAX. The unit is second.

Default value: 300

NOTE:

The unit can only be second.

Currently, primary/standby/secondary deployment is not supported by default.

catchup2normal_wait_time

Parameter description: Specifies the maximum duration that the primary server is blocked during the data catchup on the standby server in the case of a single synchronous standby server.

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

Value range: an integer ranging from -1 to 10000. The unit is ms.

The value -1 indicates that the primary server is blocked until the data catchup on the standby server is complete.
The value 0 indicates that the primary server is not blocked during the data catchup on the standby server.
Other values indicate the maximum duration that the primary server is blocked during the data catchup on the standby server. For example, if this parameter is set to 5000, the primary server is blocked until the data catchup on the standby server is complete in 5s.

Default value: -1

sync_config_strategy

Parameter description: Specifies the strategy for synchronizing configuration files between the primary and standby servers, and the standby and cascaded standby servers.

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

Value range: enumerated values

all_node: If this parameter is set to all_node on a primary server, configuration files on the primary server can be automatically synchronized to all standby servers. If this parameter is set to all_node on a standby server, the current standby server is allowed to send a synchronization request to the primary server and configuration files on the current standby server can be automatically synchronized to all cascaded standby servers. If this parameter is set to all_node on a cascaded standby server, the current cascaded standby server is allowed to send a synchronization request to its standby server.
only_sync_node: If this parameter is set to only_sync_node on a primary server, configuration files on the primary server can be automatically synchronized to only all standby servers. If this parameter is set to only_sync_node on a standby server, the current standby server is allowed to send a synchronization request to the primary server and configuration files on the current standby server cannot be automatically synchronized to all cascaded standby servers. If this parameter is set to only_sync_node on a cascaded standby server, the current cascaded standby server is allowed to send a synchronization request to its standby server.
none_node: If this parameter is set to none_node on a primary server, configuration files on the primary server cannot be automatically synchronized to only all standby servers. If this parameter is set to none_node on a standby server, the current standby server is not allowed to send a synchronization request to the primary server and configuration files on the current standby server cannot be automatically synchronized to all cascaded standby servers. If this parameter is set to none_node on a cascaded standby server, the current cascaded standby server is not allowed to send a synchronization request to its standby server.

Default value: all_node

NOTICE:

In a MogDB database instance that contains a primary node, a standby node, and a cascaded standby node, the primary node is a sender relative to the standby node and the standby node is a receiver relative to the primary node, while the standby node is a sender relative to the cascaded standby node and the cascaded standby node is a receiver relative to the standby node.

The sender actively synchronizes the configuration file to the receiver, and the receiver requests the sender to synchronize the configuration file, which are two independent events, so that the configuration files are synchronized. If you do not want to synchronize configuration files, set this parameter to none_node on the receiver. If the sender is a standby node, set this parameter to none_node only. If the sender is a primary node, set this parameter to none_node when the primary node does not synchronize with any standby node; or set this parameter to only_sync_node when the primary node synchronizes with synchronous standby nodes only and does not synchronize with asynchronous standby nodes.

To be specific, the sender sends a configuration file which directly overwrites the corresponding parameter in the configuration file of the receiver. After the policy for synchronizing configuration files is set, even if you modify configuration parameters of the receiver, the modification does not take effect because the sender immediately overwrites these parameters.

The following configuration parameters are not synchronized even if the policy for synchronizing configuration files is set: application_name, archive_command, audit_directory, available_zone, comm_control_port, comm_sctp_port, listen_addresses, log_directory, port, replconninfo1, replconninfo2, replconninfo3, replconninfo4, replconninfo5, replconninfo6, replconninfo7, replconninfo8, replconninfo9, replconninfo10, replconninfo11, replconninfo12, replconninfo13, replconninfo14, replconninfo15, replconninfo16, replconninfo17, replconninfo18, ssl, ssl_ca_file, ssl_cert_file, ssl_ciphers, ssl_crl_file, ssl_key_file, ssl_renegotiation_limit, ssl_cert_notify_time, synchronous_standby_names, local_bind_address, perf_directory, query_log_directory, asp_log_directory, streaming_router_port, enable_upsert_to_merge, archive_dest, recovery_min_apply_delay, and sync_config_strategy.

enable_save_confirmed_lsn

Parameter description: If this parameter is enabled, the primary node flushes the location that has achieved majority consistency with the current synchronous standby node during each transaction to a disk. When the primary node is faulty and the original primary node functions as the standby node to initiate a build request, the system checks whether the same confirmed LSN exists on the source node (new primary node). If it does not exist, the build fails to prevent the data of the original primary node from being overwritten by the build.

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

Value range: Boolean

on: indicates that this function is enabled. In the scenario where one primary node and multiple standby nodes are configured and a synchronous standby node is configured, each time the primary node performs a data change transaction operation (DML/DDL), and the primary node waits to reach a majority consistency location with the synchronous standby node, flushes the location that has achieved majority consistency with the current synchronous standby to disk. The persistent file corresponds to the status file of the replication slot of the synchronous standby node. If this parameter is enabled, both automatic build and incremental build in unspecified schema are affected. When the primary node is faulty and the original primary node functions as the standby node, the system checks whether the same confirmed LSN exists on the source node (new primary node). If it does not exist, the build fails to prevent the data of the original primary node from being overwritten by the build.
off: indicates that this function is disabled. The behavior of the primary node remains unchanged when a transaction is committed. The behavior of automatic build and incremental build remains unchanged. In the scenario where one primary node and multiple standby nodes are configured and asynchronous standby nodes are configured, if the primary node suddenly breaks down and the majority consistency location (such as LSN100) of the primary node is not synchronized to the asynchronous standby node, the asynchronous standby node is forcibly started as the new primary node. If some transaction operations are performed on the new primary node, the data on the new primary node overwrites LSN100. In this case, if the original primary node is used as the standby node and a build request is initiated, the primary node loses the service data of LSN100 that has reached the latest majority consistency location.

Default value: off

NOTICE:

If most_available_sync is set to on and all synchronous standby nodes are faulty, this function does not take effect. This is because no synchronous standby can trigger the persistence of the LSN.

This function affects only incremental build or automatic build without specifying the build mode. If you forcibly specify the full build mode, this function does not take effect.

If files in pg_replslot of the primary node are manually deleted or damaged before the build command is executed, this function does not take effect.

After this function is enabled, if the primary node is stopped while waiting for the standby node to achieve majority consistency, the system does not display a message indicating that the transaction has been committed locally and may not be synchronized to the remote node. This prevents upper-layer services from considering that data has been consistent.

After this function is enabled, the synchronization waiting time is prolonged due to persistent data. As a result, the performance of the primary and standby clusters with synchronous standby nodes is affected. According to the test data, the performance decreases by about 20% compared with that when this function is disabled.

hadr_recovery_time_target

Parameter description: Setting hadr_recovery_time_target in streaming disaster recovery mode enables the standby database instance to complete log writes and playback.

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

Value range: Integer, 0 to 3600 (seconds)

0 means that log flow control is not enabled, and 1~3600 means that the standby can complete log writing and playback within hadr_recovery_time_target time, which can ensure that the log writing and playback can be completed in hadr_recovery_time_target seconds when the primary database instance is switched with the standby database instance and ensure that the standby database instance If the hadr_recovery_time_target is set too small, it will affect the performance of the host, and if it is set too large, it will lose the flow control effect.

Default value: 0

hadr_recovery_point_target

Parameter description: Setting hadr_recovery_point_target in streaming disaster recovery mode enables the rpo time for the standby database instance to complete log swiping.

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

Value range: Integer, 0 to 3600 (seconds)

0 means that log flow control is not turned on, and 1~3600 means that the standby machine can complete the swiping of logs within hadr_recovery_point_target time, which can ensure that the log gap between the main database instance and the standby database instance when switching can be within hadr_recovery_point_target seconds, and guarantee that the standby database instance rises to the main log volume. If the hadr_recovery_point_target is set too small, it will affect the performance of the host, and if it is set too large, it will lose the flow control effect.

Default value: 0

hadr_super_user_record_path

Parameter description: This parameter is a streaming offsite disaster recovery parameter that indicates the path to the encrypted file storage for the hadr_disaster user in the standby database instance.

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

Modification Suggestion: This parameter is automatically set by the Streaming Disaster Tolerance Password Delivery Tool and does not need to be manually added by the user.

Value range: String

Default value: NULL

NOTICE:

In a database instance that contains a host, a spare, and a cascaded spare, the host is the sender with respect to the spare, the spare is the receiver with respect to the host, the spare is the sender with respect to the cascaded spare, and the cascaded spare is the receiver with respect to the spare.

The sender's initiative to synchronize the configuration file with the receiver and the receiver's request to synchronize the configuration file with the sender are two separate events, both of which synchronize the configuration file. If you do not want the configuration file to be synchronized, you need to configure the receiving end to be none_node, the sending end can only be configured to be none_node if it is a standby, the sending end can only be configured to be none_node if it is a host, the host will not be synchronized with all the standbys if it is configured to be none_node, and it will be synchronized with the synchronized standby only if it is only_sync_node, not with the asynchronous standby.

Configuration parameter synchronization is specifically manifested in that the sender sends a configuration file that directly overrides the corresponding parameters in the receiver's configuration file. If you set a policy that the configuration file needs to be synchronized, after modifying the configuration parameters on the receiving end, the sending end will immediately overwrite the configuration parameters on the receiving end, so that the modifications on the receiving end do not take effect.

Even if you set a policy that the configuration file needs to be synchronized, there are still some configuration parameters that will not be synchronized. Included: “application_name”, “archive_command”, “audit_directory”, “available_zone”, “comm_control_port”, “comm_sctp_port”, “listen_addresses”, “log_directory”, “port”, “replconninfo1”, “replconninfo2”, “replconninfo3”, “replconninfo4”, “replconninfo5”, “replconninfo6”, “replconninfo7”, “replconninfo8”, “replconninfo9”, “replconninfo10”, “replconninfo11”, “replconninfo12”, “replconninfo13”, “replconninfo14”, “replconninfo15”, “replconninfo16”, “replconninfo17”, “replconninfo18”, “ssl”, “ssl_ca_file”, “ssl_cert_file”, “ssl_ciphers”, “ssl_crl_file”, “ssl_key_file”, “ssl_renegotiation_limit”, “ssl_cert_notify_time”, “synchronous_standby_names”, “local_bind_address”, “perf_directory”, “query_log_directory”, “asp_log_directory”, “streaming_router_port”, “enable_upsert_to_merge”, “archive_dest”, “recovery_min_apply_delay”, “sync_config_strategy”.

pgxc_node_name

Parameter description: Specifies the name of a node.

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

When a standby node requests to replicate logs on the primary node, if the application_name parameter is not set, the pgxc_node_name parameter is used as the name of the streaming replication slot of the standby node on the primary node. The streaming replication slot is named in the following format: Value of this parameter_IP address of the standby node_Port number of the standby node. The IP address and port number of the standby node are obtained from the IP address and port number of the standby node specified by the replconninfo parameter. The maximum length of a streaming replication slot name is 61 characters. If the length of the concatenated string exceeds 61 characters, the truncated pgxc_node_name will be used for concatenation to ensure that the length of the streaming replication slot name is less than or equal to 61 characters.

Note: After this parameter is modified, the database instance will fail to be connected. You are advised not to modify this parameter.

Value range: a string

Default value: current node name