Improved memory management in Aurora PostgreSQL
Aurora PostgreSQL now includes advanced memory management capabilities to optimize database performance and resilience under varying workloads. These improvements help Aurora PostgreSQL maintain consistent availability and responsiveness, even during periods of high memory demand.
This feature is available and enabled by default in the following Aurora PostgreSQL versions:
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15.3 and all higher versions
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14.8 and higher versions
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13.11 and higher versions
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12.15 and higher versions
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11.20 and higher versions
When customer workloads use up all available free memory, the operating system may restart the database to protect resources, leading to temporary unavailability. The new memory management improvements in Aurora PostgreSQL proactively cancel certain transactions when the system experiences high memory pressure, helping to maintain database stability.
The key features of improved memory management is as follows:
Cancelling database transactions that request more memory when the system is approaching critical memory pressure.
The system is said to be under critical memory pressure, when it exhausts all the physical memory and is about to exhaust the swap. In these circumstances, any transaction that requests memory will be cancelled in an effort to immediately reduce memory pressure in the DB instance.
Essential PostgreSQL launchers and background workers such as autovacuum workers are always protected.
Handling memory management parameters
To turn on memory management
This feature is turned on by default. An error message is displayed when a transaction is cancelled due to insufficient memory as shown in the following example:
ERROR: out of memory Detail: Failed on request of size 16777216.
To turn off memory management
To turn off this feature, connect to the Aurora PostgreSQL DB cluster with psql and use the SET statement for the parameter values as mentioned below.
Note
We recommend that you keep memory management enabled. This helps prevent potential out-of-memory errors that may lead to workload-induced database restarts due to memory exhaustion.
The following table shows how to turn off the memory management feature for the different Aurora PostgreSQL versions:
| Aurora PostgreSQL versions | Parameter | Default | Command to turn off memory management at session level |
|---|---|---|---|
11.20, 11.21, 12.15, 12.16, 13.11, 13.12, 14.8, 14.9, 15.3, 15.4 |
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12.17, 13.13, 14.10, 15.5, and higher versions |
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Note
The rds.memory_allocation_guard parameter has been deprecated in Aurora PostgreSQL 12.17, 13.13, 14.10, 15.5, and higher versions.
Setting the values of these parameters in the DB cluster parameter group prevents the queries from being canceled. For more information about DB cluster parameter group, see Parameter groups for Amazon Aurora.
Limitation
This feature is not supported in db.t3 and db.serverless instance classes.
