🛢DBMS: Fragmentation (Definitions)

"Describes the effect to a database that is spread out in various pieces across multiple different devices. Fragmentation can also occur in a database in which the pages are not in physical order." (Owen Williams, "MCSE TestPrep: SQL Server 6.5 Design and Implementation", 1998)

"A condition that occurs when data modifications are made. You can reduce fragmentation and improve read-ahead performance by dropping and re-creating a clustered index. DBCC DBREINDEX, which can rebuild all of the indexes for a table in one statement, is often used to defragment tables." (Microsoft Corporation, "SQL Server 7.0 System Administration Training Kit", 1999)

"Fragmentation often occurs in databases when frequent or large data modifications are made. SQL Server 2000 provides methods for reducing fragmentation and improving read-ahead performance by dropping and re-creating a clustered index." (Anthony Sequeira & Brian Alderman, "The SQL Server 2000 Book", 2003)

"Occurs when data modifications are made. You can reduce fragmentation and improve read-ahead performance by dropping and re-creating a clustered index." (Thomas Moore, "EXAM CRAM™ 2: Designing and Implementing Databases with SQL Server 2000 Enterprise Edition", 2005)

"When a page fills with data, SQL Server must take half of the data from the full page and move it to a new page to make room for more data. When a new page is created, then the pages inside the database are no longer contiguous. This condition is called fragmentation ." (Joseph L Jorden & Dandy Weyn, "MCTS Microsoft SQL Server 2005: Implementation and Maintenance Study Guide - Exam 70-431", 2006)

"A process that occurs when data modifications are made. It is possible to reduce fragmentation and improve read-ahead performance by dropping and re-creating a clustered index." (Thomas Moore, "MCTS 70-431: Implementing and Maintaining Microsoft SQL Server 2005", 2006)

"A process that degrades performance because of data not being contiguous as a result of data being modified." (Victor Isakov et al, "MCITP Administrator: Microsoft SQL Server 2005 Optimization and Maintenance (70-444) Study Guide", 2007)

"A doubly linked series of pages whose logical order does not equal the physical order." (Marilyn Miller-White et al, "MCITP Administrator: Microsoft® SQL Server™ 2005 Optimization and Maintenance 70-444", 2007)

"In databases, indexes can be fragmented similar to how a hard drive can be fragmented. A fragmented index results in slower performance of the database. Fragmentation can be reduced by setting a fill factor on an index so it has empty space. Fragmented indexes can be defragmented by using REORGANIZE (keeps the index online) or by using REBUILD (which defaults to offline but can be run online)." (Darril Gibson, "MCITP SQL Server 2005 Database Developer All-in-One Exam Guide", 2008)

"The separation of the index into pieces as a result of inserts and deletions in the index." (Sybase, "Open Server Server-Library/C Reference Manual", 2019)