Postgresql – How to set up Amazon RDS parameter group for Postgres

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I'm trying to create a parameter group in Amazon Web Services for an Postgres 9.5 RDS instance. I'm a little confused by the units being used for things such as shared_buffers and min_wal_size. Typically these would be specified in postgresql.conf with units, like 4GB or 128kB. If I enter the same in AWS I get an error that the value I specified was invalid, but strictly numeric values seem to be fine. Does anyone know what units these parameters are expecting?

Best Answer

Amazon RDS documentation provides a table of units for each parameter under the "Working with PostgreSQL Parameters" topic. Units are also usually included in the description of each parameter in the parameter group edit UI from the Amazon RDS web console.

min_wal_size (Postgres 9.5 Parameter Group Family)

  • Default: 16
  • Units: MB
  • Allowed Values: 2-201326592
  • Description: (16MB) Sets the minimum size to shrink the WAL to.

shared_buffers (Postgres 9.5 Parameter Group Family)

  • Default: {DBInstanceClassMemory/32768}
  • Units: 8kB
  • Allowed Values: 16-1073741823
  • Description: (8kB) Sets the number of shared memory buffers used by the server.

Regarding shared_buffers specifically, the documentation has this to say:

Note that some parameters use units that you might not be familiar with; for example, shared_buffers sets the number of 8 KB shared memory buffers used by the server.

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