Deletion is the process whereby data is removed from active files and other data storage structures on computers and rendered inaccessible except using special data recovery tools designed to recover deleted data. Deletion occurs in several levels on mode

Deletion is the process whereby data is removed from active files and other data storage structures on computers and rendered inaccessible except using special data recovery tools designed to recover deleted data. Deletion occurs in several levels on modern computer systems: (a) File level deletion: Deletion on the file level renders the file inaccessible to the operating system and normal application programs and marks the space occupied by the file's directory entry and contents as free space, available to reuse for data storage. (b) Record level deletion: Deletion on the record level occurs when a data structure, like a database table, contains multiple records; deletion at this level renders the record inaccessible to the database management system (DBMS) and usually marks the space occupied by the record as available for reuse by the DBMS, although in some cases the space is never reused until the database is compacted. Record level deletion is also characteristic of many e-mail systems. (c) Byte level deletion: Deletion at the byte level occurs when text or other information is deleted from the file content (such as the deletion of text from a word processing file); such deletion may render the deleted data inaccessible to the application intended to be used in processing the file, but may not actually remove the data from the file's content until a process such as compaction or rewriting of the file causes the deleted data to be overwritten.