Core conceptsbeginner
Shared buffers
The shared-memory cache PostgreSQL uses to hold heap and index pages, reducing how often it must read from the operating system and disk.
What this means
Postgres's own in-memory shelf for the table and index pages it's working with. Rather than asking the operating system and disk for the same page over and over, it keeps hot pages on this shared shelf and reuses them. The bigger the shelf, the more reads are answered straight from memory.
Why it matters operationally
It is the most discussed memory setting for good reason: it shapes cache hit ratio and the read latency profile of the whole instance.
Related errors
Mentioned from
Where it lives in the source
src/backend/storage/buffer/bufmgr.c