Database server thread access to shared buffers

Database server threads access shared buffers through a system of queues, using mutexes and locks to synchronize access and protect data.

FIFO/LRU queues
A buffer holds data for the purpose of caching. The database server uses the least-recently used (LRU) queues to replace the cached data. HCL Informix® also has a first-in first-out (FIFO) queue. When you set the number of LRU queues, you are actually setting the number of FIFO/LRU queues.
Read-ahead operations
The database server automatically reads several pages ahead of the current pages that are being processed for a query, unless you disable automatic read ahead operations. Reading ahead enables applications to run faster because they spend less time waiting for disk I/O.
Database server thread access to buffer pages
The database server uses shared-lock buffering to allow more than one database server thread to access the same buffer concurrently in shared memory.

Parent topic: Shared memory