effective_cache_size v16

Parameter type: Integer

Default value: 128MB

Range: 8kB to 17179869176kB

Minimum scope of effect: Per session

When value changes take effect: Immediate

Required authorization to activate: Session user

Sets the planner's assumption about the effective size of the disk cache that's available to a single query. This assumption is factored into estimates of the cost of using an index. A higher value makes it more likely index scans are used. A lower value makes it more likely sequential scans are used.

When setting this parameter, consider both EDB Postgres Advanced Server’s shared buffers and the portion of the kernel's disk cache that are used for EDB Postgres Advanced Server data files. Also, consider the expected number of concurrent queries on different tables, since they have to share the available space.

This parameter doesn't affect the size of shared memory allocated by EDB Postgres Advanced Server, and it doesn't reserve kernel disk cache. Use it only for estimating.

If this parameter is set too low, the planner might decide not to use an index even when it's helpful to do so. Setting effective_cache_size to 50% of physical memory is a normal, conservative setting. A more aggressive setting is approximately 75% of physical memory.