dets

DETS, short for Disk Erlang Term Storage, is a simple on-disk storage facility shipped with the Erlang runtime. It provides persistent storage for Erlang terms by exposing a table-like API similar to ETS, but backed by a file on disk.

A DETS table stores records as key-value pairs (key, value). You open a file to hold the table with dets:open/2, and then perform operations such as dets:insert/2, dets:lookup/2, and dets:delete/2. The API is designed to be straightforward and conceptually similar to ETS, enabling familiar patterns while persisting data between runs.

DETS is intended for lightweight persistence and small datasets. It is not designed for high-concurrency workloads or large-scale deployments. It lacks the richer transactional options of Mnesia and is generally slower than in-memory ETS for frequent reads. Because the table is persisted on disk, proper file open/close handling is required to ensure data integrity; abrupt termination can leave the file in an inconsistent state unless the table is closed properly.

DETS is commonly used for simple configuration data, caches, or temporary persistence in small applications or during prototyping. For robust, multi-node or high-volume storage, Erlang's Mnesia or external databases are recommended.

See also Mnesia, ETS, Erlang, OTP.