Do you know the datastructure utilized in DBMS like Oracle,MySQL &lifier Sqlite for storing and locating records.

Often a clever implementation of B-Trees

In the above linked wikipedia article:

A B --tree of order m (the utmost quantity of children for every node) is really a tree which satisfies the next qualities:

  1. Every node has for the most part m children.
  2. Every node (except root leaving) has a minimum of m⁄2 children.
  3. The main has a minimum of two children if it's not a leaf node.
  4. All leaves come in exactly the same level, and carry information.
  5. A non-leaf node with k children consists of k–1 secrets

The benefits of that are that data could be utilized in logarithmic time, associated with pension transfer search trees (for example standard binary trees), however the timing qualities be more effective within the average situation.

MySQL has pluggable storage systems. This means that engine may use different storages. It presently has 5-6 of these which you can use. And also, since it's free, you can observe how it's done.

SQLite uses it's own B-Tree implementation with journaling. Free - you can try it.

Firebird and Interbase are utilizing B-Trees with multi-record versioning systems for storage. Firebird is free. Worth searching.

Can't tell for Oracle, MS SQL Server or any other proprietary database systems, given that they keep storage information secret.