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<@U0A71G31CDV> how to check backend configs
# questions-and-troubleshooting
z
@Rocky how to check backend configs
r
To check backend (BE) configurations in StarRocks, you can use the following methods: 1. Using SQL (Recommended) You can query the 
information_schema.be_configs
table to view configuration parameters for all BE nodes in the cluster. This is the most convenient way to search for specific parameters.
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sql
-- View all configurations for all BEs
SELECT * FROM information_schema.be_configs;

-- Search for a specific configuration parameter
SELECT * FROM information_schema.be_configs WHERE NAME LIKE '%tablet%';
2. Using HTTP API Each BE node provides an HTTP endpoint that returns its current configuration. This is useful for checking a specific node directly.
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bash
curl http://<BE_IP>:<BE_HTTP_PORT>/varz
* BE_IP: The IP address of the BE node. * BE_HTTP_PORT: The 
be_http_port
(default is 
8040
). 3. Using SHOW BACKENDS To check basic status information (ports, disk usage, memory limits, and version) rather than internal configuration parameters, use:
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sql
SHOW BACKENDS;
Note on Modification * To check if a parameter can be modified dynamically (without a restart), look at the 
MUTABLE
column in 
information_schema.be_configs
. * To modify a BE configuration dynamically, use the 
update_config
API:
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bash
    curl -X POST http://<BE_IP>:<BE_HTTP_PORT>/api/update_config?parameter_name=value
* For persistent changes, you must update the 
be.conf
file on each BE node. References • administration/management/BE_configuration.md • administration/management/FE_configuration.md • sql-reference/sql-statements/cluster-management/config_vars/ADMIN_SHOW_CONFIG.md • sql-reference/information_schema/be_configs.md • sql-reference/sql-statements/cluster-management/nodes_processes/SHOW_BACKENDS.md • sql-reference/sql-statements/cluster-management/nodes_processes/SHOW_PROC.md
z
@Rocky no via admin show backend?
r
No, 
ADMIN SHOW CONFIG
(or 
ADMIN SHOW FRONTEND CONFIG
) only displays FE configuration items. There is no equivalent 
ADMIN SHOW BACKEND
command for BE configurations. To view BE internal configuration parameters, you must use one of the following: 1. SQL: Query the 
information_schema.be_configs
table. This is the most direct way to see BE-specific settings like 
tablet_writer_open_rpc_timeout_sec
or 
storage_flood_stage_usage_percent
.
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sql
    SELECT * FROM information_schema.be_configs;
2. HTTP API: Request the 
/varz
endpoint from a specific BE.
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bash
    curl http://<BE_IP>:<BE_HTTP_PORT>/varz
Why the confusion? * 
SHOW BACKENDS
: Shows node status (Alive, IP, Disk Usage, Memory Limit), but not internal configuration parameters. * 
ADMIN SHOW CONFIG
: Only supports FE parameters. Even though it is a cluster-level command, the documentation specifies it currently only returns Frontend configuration items can display FE items. References • sql-reference/information_schema/be_configs.md • sql-reference/sql-statements/cluster-management/config_vars/ADMIN_SHOW_CONFIG.md • sql-reference/sql-statements/cluster-management/nodes_processes/SHOW_BACKENDS.md References • sql-reference/information_schema/be_configs.md • faq/operation_maintenance_faq.md • sql-reference/sql-statements/cluster-management/nodes_processes/SHOW_BACKENDS.md • sql-reference/sql-statements/cluster-management/nodes_processes/SHOW_PROC.md
z
@Rocky where should I find variable mem_limit then?
r
The 
mem_limit
parameter is a BE configuration (not an FE variable). You can find it in the following places: 1. View via SQL (Recommended) You can query the current value for all BE nodes using the 
information_schema.be_configs
table:
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sql
SELECT * FROM information_schema.be_configs WHERE NAME = 'mem_limit';
2. View via SHOW BACKENDS The 
SHOW BACKENDS
command displays the calculated physical memory limit for each node in the 
MemLimit
column. Note that if 
mem_limit
is set as a percentage (e.g., 
90%
), this command shows the actual byte value.
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sql
SHOW BACKENDS;
3. View via HTTP API You can check it directly from a specific BE node:
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bash
curl http://<BE_IP>:<BE_HTTP_PORT>/varz | grep mem_limit
Important Details about `mem_limit`: * Default: 
90%
of the server's total memory. * Type: Can be a percentage (e.g., 
80%
) or a physical limit (e.g., 
100G
). * Mutability: It is not mutable (Is mutable: No). This means you cannot change it dynamically via SQL or API; you must modify the 
be.conf
file and restart the BE for changes to take effect. References • administration/management/BE_configuration.md • sql-reference/information_schema/be_configs.md • sql-reference/sql-statements/cluster-management/nodes_processes/SHOW_BACKENDS.md References • administration/management/BE_configuration.md
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