Check cluster parameters|V4.2.5| docs|Distributed Database

Check cluster parameters

Last Updated：2025-01-02 01:58:39 Updated

This topic describes how to view and modify cluster parameters by using SQL statements.

View parameters

Cluster parameters

Parameter	Description	Recommended value
memory_limit_percentage	The percentage of the total available memory to the total memory of the system. Value range: [10, 90].	80
server_permanent_offline_time	The timeout period for a server. If no heartbeat message is sent from a server within the period, the server is considered permanently offline. Data replicas on a permanently offline server need to be automatically supplemented. Value range: [20s, +∞).	7200s
clog_sync_time_warn_threshold	The warning threshold of the transaction log synchronization duration. If the synchronization duration exceeds this threshold, a WARN log is generated. Value range: [1ms, 10000ms].	1s
large_query_threshold	The threshold of the query execution duration. A request may be suspended if its execution time exceeds this threshold. A suspended request is considered a large query and is processed by following the large query scheduling strategy. Value range: [1ms, +∞).	5s
trace_log_slow_query_watermark	The threshold of the query execution duration. A query whose execution duration exceeds this threshold is considered a slow query. Trace logs of slow queries are written to system logs. Value range: [1ms, +∞).	1s
autoinc_cache_refresh_interval	The refresh interval for the auto-increment column cache. Value range: [100ms, +∞).	4200s
default_compress_func	The default algorithm for compressing table data. You can also specify another compression algorithm when you create a table. Valid values: `none`, `lz4-1.0`, `snappy-1.0`, `zstd-1.0`, and `zstd-1.3.8`.	zstd_1.0
syslog_io_bandwidth_limit	The maximum I/O bandwidth available for system logs. If this value is reached, the remaining system logs are discarded.	5 MB
memstore_limit_percentage	The percentage of the memory occupied by the MemStore to the total available memory of a tenant. Value range: [1, 99].	50
system_memory	The memory size reserved by the system for the `sys500` tenant. Value range: [0M, +∞).	50 GB
resource_hard_limit	Specifies how resource units are allocated. During the allocation of resources such as CPU cores and memory, the total resource volume is the actual volume multiplied by the specified value in percentage. The proportion of the final allocated server resource volume cannot exceed the value of `resource_hard_limit`. Value range: [100, 10000].	100
syslog_level	The level of system logs. Valid values: `DEBUG`, `TRACE`, `INFO`, `WARN`, `USER-ERR`, and `ERROR`.	INFO
data_disk_usage_limit_percentage	The maximum usage of the data disk. When the usage exceeds this threshold, data can no longer be migrated into the data disk. Value range: [50, 100].	95
enable_perf_event	Specifies whether to enable the information collection feature for performance events. Valid values: `True` and `False`.	True
enable_sql_audit	Specifies whether to enable SQL audit. Valid values: `True` and `False`.	True

Query the values of parameters from views

You can query the values of cluster parameters from the GV$OB_PARAMETERS view in the sys tenant. Here is an example:

SELECT SVR_IP,ZONE,NAME,VALUE FROM OCEANBASE.GV$OB_PARAMETERS WHERE NAME IN ("memory_limit_percentage", "server_permanent_offline_time", "clog_sync_time_warn_threshold", "large_query_threshold", "trace_log_slow_query_watermark", "autoinc_cache_refresh_interval", "default_compress_func", "syslog_io_bandwidth_limit", "memstore_limit_percentage", "system_memory", "resource_hard_limit", "syslog_level", "data_disk_usage_limit_percentage", "enable_perf_event", "enable_sql_audit");

Here is an example:

obclient [(none)]> SELECT SVR_IP,ZONE,NAME,VALUE FROM OCEANBASE.GV$OB_PARAMETERS WHERE NAME IN ("memory_limit_percentage", "server_permanent_offline_time", "clog_sync_time_warn_threshold", "large_query_threshold", "trace_log_slow_query_watermark", "autoinc_cache_refresh_interval", "default_compress_func", "syslog_io_bandwidth_limit", "memstore_limit_percentage", "system_memory", "resource_hard_limit", "syslog_level", "data_disk_usage_limit_percentage", "enable_perf_event", "enable_sql_audit");

The return result is as follows:

+-----------------+-------+----------------------------------+------------+
| SVR_IP          | ZONE  | NAME                             | VALUE      |
+-----------------+-------+----------------------------------+------------+
| xxx.xxx.xxx.xxx | zone1 | data_disk_usage_limit_percentage | 90         |
| xxx.xxx.xxx.xxx | zone1 | clog_sync_time_warn_threshold    | 100ms      |
| xxx.xxx.xxx.xxx | zone1 | resource_hard_limit              | 100        |
| xxx.xxx.xxx.xxx | zone1 | server_permanent_offline_time    | 3600s      |
| xxx.xxx.xxx.xxx | zone1 | memstore_limit_percentage        | 50         |
| xxx.xxx.xxx.xxx | zone1 | large_query_threshold            | 5s         |
| xxx.xxx.xxx.xxx | zone1 | autoinc_cache_refresh_interval   | 3600s      |
| xxx.xxx.xxx.xxx | zone1 | memory_limit_percentage          | 80         |
| xxx.xxx.xxx.xxx | zone1 | syslog_io_bandwidth_limit        | 30MB       |
| xxx.xxx.xxx.xxx | zone1 | syslog_level                     | WDIAG      |
| xxx.xxx.xxx.xxx | zone1 | default_compress_func            | zstd_1.3.8 |
| xxx.xxx.xxx.xxx | zone1 | enable_perf_event                | True       |
| xxx.xxx.xxx.xxx | zone1 | enable_sql_audit                 | True       |
| xxx.xxx.xxx.xxx | zone1 | trace_log_slow_query_watermark   | 1s         |
| xxx.xxx.xxx.xxx | zone1 | system_memory                    | 30G        |
+-----------------+-------+----------------------------------+------------+
15 rows in set

Query the values of parameters by using the SHOW statement

You can execute the following SQL statement in the sys tenant to query the values of cluster parameters:

SHOW PARAMETERS LIKE '$parameters_name';

Here, $parameters_name is the name of the cluster parameter.

Here is an example:

obclient [(none)]> SHOW PARAMETERS LIKE 'enable_sql_audit';

The return result is as follows:

+-------+----------+----------------+----------+------------------+-----------+-------+---------------------------------------------------------------------------------------------------------------+----------+---------+---------+-------------------+
| zone  | svr_type | svr_ip         | svr_port | name             | data_type | value | info                                                                                                          | section  | scope   | source  | edit_level        |
+-------+----------+----------------+----------+------------------+-----------+-------+---------------------------------------------------------------------------------------------------------------+----------+---------+---------+-------------------+
| zone1 | observer | xxx.xxx.xxx.xxx |     2882 | enable_sql_audit | NULL      | True  | specifies whether SQL audit is turned on. The default value is TRUE. Value: TRUE: turned on FALSE: turned off | OBSERVER | CLUSTER | DEFAULT | DYNAMIC_EFFECTIVE |
+-------+----------+----------------+----------+------------------+-----------+-------+---------------------------------------------------------------------------------------------------------------+----------+---------+---------+-------------------+
1 row in set

Modify cluster parameters

You can modify cluster parameters by using SQL statements.

The following example shows the syntax for modifying a parameter. If you want to modify two or more parameters at the same time, separate them with commas (,).

ALTER SYSTEM SET param_name = expr
  [COMMENT 'text']
  [PARAM_OPTS]
  [TENANT = 'tenantname'];    

PARAM_OPTS:
  [ZONE='zone' | SERVER='server_ip:rpc_port']

Take note of the following points when you use this statement:

You can use PARAM_OPTS to specify additional qualifiers, such as the zone or server, when you modify the parameters.
ALTER SYSTEM allows you to specify a zone or a server, but not both. You can specify only one zone for ZONE and one server for SERVER, if these parameters are to be specified.
You cannot set cluster-level parameters in a user tenant or in the sys tenant by specifying a user tenant. For example, the ALTER SYSTEM SET memory_limit='100G' TENANT='test_tenant' statement will cause an error because memory_limit is a cluster-level parameter.

Here is an example:

Change the value of server_permanent_offline_time to 7200s:

obclient [(none)]> ALTER SYSTEM SET server_permanent_offline_time = '7200s';

References

If you are using OceanBase Cloud Platform (OCP) to manage your OceanBase cluster, you can also perform unified parameter management in the OCP console, including viewing parameters, modifying parameters, and viewing parameter modification history. For more information, see View parameters.
For more information about cluster parameters, see Overview.