Additional engine types include: Information in a database is stored in the form of bits, laid out into data structures on storage hardware.
In practice, only a very small percentage of addresses are kept as initial reference points, which also require storage.
Inside of a contemporary computer hosting a DBMS, most of the "database" part resides, partially replicated, in volatile storage.
These data are read from and written to memory, typically through a computer bus, which is usually a volatile storage component.
The drives may be connected to magnetic tapes, on which the least active parts of a large database may reside.
[1] Common examples are the following: In contrast to conventional row-orientation, relational databases can also be column-oriented or correlational in the way they store data in any particular structure.
In general, substantial performance improvement is gained if different types of database objects that are usually utilized together are laid in storage in proximity, being "clustered".
This usually allows to retrieve needed related objects from storage in minimum number of input operations (each sometimes substantially time-consuming).
Even for in-memory databases clustering provides performance advantage due to common utilization of large caches for input-output operations in memory, with similar resulting behavior.
The many types of indexes share the common property that they reduce the need to examine every entry when running a query.