Modifying Parameters of an RDS for PostgreSQL Instance

You can modify parameters in a custom parameter template to optimize RDS database performance.

You can change parameter values in custom parameter templates only and cannot change parameter values in default parameter templates.

The following are the key points you should know when using parameters:

Modifying instance parameters: When you modify dynamic parameters on the Parameters page of a target DB instance and save the modifications, the modifications take effect immediately regardless of the Effective upon Reboot setting. When you modify static parameters on the Parameters page of a target DB instance and save the modifications, the modifications take effect only after you manually reboot the target DB instance.
Modifying parameter template parameters: When you modify parameters in a custom parameter template on the Parameter Templates page and save the modifications, the modifications take effect only after you apply the parameter template to DB instances. When you modify static parameters in a custom parameter template on the Parameter Templates page and save the modifications, the modifications take effect only after you apply the parameter template to DB instances and manually reboot the DB instances. For operation details, see Applying a Parameter Template.

When you modify a parameter, the time when the modification takes effect is determined by the type of the parameter.

The RDS console displays the statuses of DB instances that the parameter template applies to. For example, if the DB instance has not yet used the latest modifications made to its parameter template, its status is Parameter change. Pending reboot. Manually reboot the DB instance for the latest modifications to take effect for that DB instance.

RDS has default parameter templates whose parameter values cannot be changed. You can view these parameter values by clicking the default parameter templates. If a custom parameter template is set incorrectly, the database startup may fail. If this happens, you can re-configure the custom parameter template based on the settings of the default parameter template.

Modifying Parameters of a DB Instance

Log in to the management console.
Click in the upper left corner and select a region.
Click in the upper left corner of the page and choose Databases > Relational Database Service.
On the Instances page, click the target DB instance.
In the navigation pane on the left, choose Parameters. On the displayed page, modify parameters as required.

Available operations are Save, Cancel, and Preview:
- To save the modifications, click Save.
- To cancel the modifications, click Cancel.
- To preview the modifications, click Preview.
In the Effective upon Reboot column:
- If the value is Yes and the DB instance status on the Instances page is Parameter change. Pending reboot, a reboot is required for the modifications to take effect.
  
  If you have modified parameters of a primary DB instance, you need to reboot the primary DB instance for the modifications to take effect. (For primary/standby DB instances, the parameter modifications are also applied to the standby DB instance.)
  
  If you have modified parameters of a read replica, you need to reboot the read replica for the modifications to take effect.
- If the value is No, the modifications take effect immediately.
After parameters are modified, you can view parameter change history by referring to Viewing Parameter Change History.

Modifying a Custom Parameter Template and Applying It to DB Instances

Log in to the management console.
Click in the upper left corner and select a region.
Click in the upper left corner of the page and choose Databases > Relational Database Service.
Choose Parameter Templates in the navigation pane on the left. On the Custom Templates page, click the target parameter template.
On the Parameters page, modify parameters as required.

Available operations are Save, Cancel, and Preview:
- To save the modifications, click Save.
- To cancel the modifications, click Cancel.
- To preview the modifications, click Preview.
After the parameter values are modified, you can click Change History to view the modification details.
Apply the parameter template to your DB instance. For details, see Applying a Parameter Template.
View the status of the DB instance to which the parameter template was applied.

If the DB instance status is Parameter change. Pending reboot, a reboot is required for the modifications to take effect.
- A DB instance reboot caused by instance class changes will not make parameter modifications take effect.
- If you have modified parameters of a primary DB instance, you need to reboot the primary DB instance for the modifications to take effect. (For primary/standby DB instances, the parameter modifications are also applied to the standby DB instance.)
- If you have modified parameters of a read replica, you need to reboot the read replica for the modifications to take effect.

FAQ

Q: Why did my changes to parameters fail to be applied to my DB instance after I rebooted the instance and the instance status remain Parameter change. Pending reboot?

A: If you change specification parameters, such as work_mem, shared_buffers, and max_connections, to large values, the instance may fail to be started. To ensure that the database runs properly, the system automatically rolls back the parameter change when the database startup fails. Check whether the new values you set are within the allowed ranges. If you do need to set specification parameters to values beyond those ranges, upgrade the instance class first. For details about how to change an instance class, see Changing a DB Instance Class.

Common Parameters

**Table 1** Common parameters
Parameter	Description	Reference
timezone	The time zone for displaying and interpreting time stamps.	How Can I Change the Time Zone?
wal_level	The level of information written to the WAL. This parameter is always set to logical for read replicas.	Does RDS for PostgreSQL Support the test_decoding Plugin?
max_connections	The maximum number of concurrent connections.	Instance Usage Suggestions