Dual-Cluster Replication Parameters

enable_roach_standby_cluster

Parameter description: Sets the instances of the standby cluster to read-only in dual-cluster mode. Only the sysadmin user can access this parameter.

This parameter is a POSTMASTER parameter. Set it based on instructions provided in Table 2.

Value range: Boolean

• on indicates that the read-only mode is enabled for the standby cluster.
• off indicates that the read-only mode is disabled for the standby cluster. In this case, the standby cluster can be read and written.

Default value: off

enable_slot_log

Parameter description: Determines whether to enable primary/standby synchronization for logical replication slots.

This parameter is a USERSET parameter. Set it based on instructions provided in Table 2.

Value range: Boolean

• on indicates that primary/standby synchronization is enabled for logical replication slots.
• off indicates that primary/standby synchronization is disabled for logical replication slots.

Default value: on

max_changes_in_memory

Parameter description: Specifies the maximum number of DML statements cached in memory for a single transaction during logical decoding.

This parameter is a POSTMASTER parameter. Set it based on instructions provided in Table 2.

Value range: an integer ranging from 1 to 2147483647

Default value: 4096

max_cached_tuplebufs

Parameter description: Specifies the upper limit of the total tuple information cached in the memory during logical decoding. You are advised to set this parameter to a value greater than or equal to twice of max_changes_in_memory.

This parameter is a POSTMASTER parameter. Set it based on instructions provided in Table 2.

Value range: an integer ranging from 1 to 2147483647

Default value: 8192

logical_decode_options_default

Parameter description: Specifies the global default value for unspecified decoding options when logical decoding starts.

This parameter is a SIGHUP parameter. Set it based on instructions provided in Table 2.

Currently, the following logical decoding options are supported: parallel-decode-num, parallel-queue-size, max-txn-in-memory, max-reorderbuffer-in-memory, and exclude-users. For the meanings of the options, see Example: Logic Replication Code.

Value range: a string of key=value characters separated by commas (,), for example, 'parallel-decode-num=4,parallel-queue-size=128,exclude-users=userA'. An empty string indicates that the default value hardcoded by the program is used.

Default value: ""

The SIGHUP parameter does not affect the started logic decoding process. The options specified by this parameter are used as the default settings for subsequent logic decoding startup, and the settings specified in the startup command are preferentially used.

The exclude-users option is different from the logic decoding startup option. You are not allowed to specify multiple blacklisted users.

logical_sender_timeout

Parameter description: Specifies the maximum waiting time for the sender to wait for the receiver to receive logical logs.

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

Value range: an integer ranging from 0 to 2147483647. The unit is ms.

Default value: 30s

RepOriginId

Parameter description: This parameter is a session-level GUC parameter. In bidirectional logical replication, set it to a non-zero value to avoid infinite data replication.

This parameter is a USERSET parameter. Set it based on Method 3 provided in Table 2.

Value range: an integer ranging from 0 to 2147483647

Default value: 0

hadr_max_size_for_xlog_receiver

Parameter description: Specifies the maximum difference between the OBS logs obtained by instances in the DR cluster and the local playback logs. If the difference is greater than the value of this parameter, the instances stop obtaining OBS logs.

This parameter is a SIGHUP parameter. Set it based on instructions provided in Table 2.

Handling suggestion: The value of this parameter is related to the local disk size. You are advised to set this parameter to 50% of the local disk size.

Value range: an integer ranging from 0 to 2147483647

Default value: 256GB

auto_csn_barrier

Parameter description: Specifies whether the barrier logging function is enabled for the primary cluster for streaming DR.

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

Value range: Boolean

• on: enabled.
• off: disabled.

Default value: off

stream_cluster_run_mode

Parameter description: Specifies whether a CN or DN belongs to the primary or standby cluster in a dual-cluster streaming DR scenario. In a single-cluster scenario, the primary cluster is selected by default.

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

Value range: enumerated values

• cluster_primary indicates that the node is in the primary cluster.
• cluster_standby indicates that the node is in the standby cluster.

Default value: cluster_primary