MEMORYONLY

MEMORYONLY is a term used in computing to describe a data storage approach in which data is kept exclusively in volatile memory (RAM) and is not persisted to non-volatile storage by default. In a memory-only configuration, applications access data with very low latency and high throughput, but the data can be lost if the system powers down or crashes unless durability mechanisms are employed.

Memory-only storage is common in in-memory databases, caches, session stores, and real-time analytics pipelines, where speed is prioritized over durability. Systems may run entirely in memory or operate as a layer on top of durable storage, with a separate persistence feature such as periodic snapshots, write-ahead logs, or disk-based backups to recover state after failures.

Architectural considerations include memory sizing, data structures, and garbage collection. Because data resides in RAM, capacity constraints are more critical than in disk-backed systems. Performance depends on CPU, memory bandwidth, and efficient memory management. Some implementations use memory-mapped files or hybrid approaches to simulate memory-only behavior while enabling recovery.

Advantages include very low latency, high throughput, and simplicity of design for transient data. Disadvantages include vulnerability to data loss, higher hardware costs for large datasets, and the need for robust backup and failover strategies. In practice, memory-only modes are often combined with durability options (checkpointing, replication, or persistent memory) to balance speed and reliability.

See also: in-memory database, cache, persistent memory, RAM disk.