{"id":2799,"date":"2015-11-10T05:23:42","date_gmt":"2015-11-10T10:23:42","guid":{"rendered":"https:\/\/academy.sqlbak.com\/?p=2799"},"modified":"2015-11-12T09:33:14","modified_gmt":"2015-11-12T14:33:14","slug":"database-page","status":"publish","type":"post","link":"https:\/\/academy.sqlbak.com\/database-page\/","title":{"rendered":"Database Page"},"content":{"rendered":"

Every piece of\u00a0data in SQL Server is stored in 8 KB database\u00a0pages. A page is a basic unit\u00a0of I\/O operation. A page starts with a 96-byte header<\/strong> in which all system information (the amount of free space, the page type, the page number, and the allocation unit ID of the object that owns the page) is stored. Another part of the page is its\u00a0body<\/strong> or data rows (8,060 bytes). The\u00a0body contains all the data in rows. The\u00a0last part of the database page is row<\/strong>\u00a0offsets<\/strong>\u00a0that are located in reverse sequence from the sequence of the rows on the page (36 bytes).<\/p>\n

\"Database<\/p>\n

Page Types<\/h2>\n

There are several types of database pages:<\/p>\n

    \n
  1. Data Page<\/strong> details how the data is stored inside the data files, database.<\/li>\n
  2. Index Page<\/strong>\u00a0contains\u00a0index entries.<\/li>\n
  3. Text and Image<\/strong>\u00a0contains textual and image data.<\/li>\n
  4. GAM<\/strong> (Global Allocation Map) and SGAM<\/strong> (Shared Global Allocation Map) contain information about whether extents are allocated.<\/li>\n
  5. PFS<\/strong> (Page Free Space) contains information about the free space available on pages and about page allocation.<\/li>\n
  6. IAM<\/strong> (Index Allocation Map) contains information about extents used by a table or index.<\/li>\n
  7. Bulk Changed Map<\/strong> contains the extent information that has been modified by bulk operations since the last BACKUP LOG.<\/li>\n
  8. Differential Changed Map<\/strong>\u00a0contains the extent information\u00a0that has changed since the last BACKUP DATABASE.<\/li>\n<\/ol>\n","protected":false},"excerpt":{"rendered":"

    Every piece of\u00a0data in SQL Server is stored in 8 KB database\u00a0pages. A page is a basic unit\u00a0of I\/O operation.<\/p>\n","protected":false},"author":10,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[157],"tags":[],"yoast_head":"\nDatabase Page - Sql Server Backup Academy<\/title>\n<meta name=\"description\" content=\"Learn about SQL Server database page\" \/>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" href=\"https:\/\/academy.sqlbak.com\/database-page\/\" \/>\n<meta property=\"og:locale\" content=\"en_US\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"Database Page - Sql Server Backup Academy\" \/>\n<meta property=\"og:description\" content=\"Learn about SQL Server database page\" \/>\n<meta property=\"og:url\" content=\"https:\/\/academy.sqlbak.com\/database-page\/\" \/>\n<meta property=\"og:site_name\" content=\"Sql Server Backup Academy\" \/>\n<meta property=\"article:published_time\" content=\"2015-11-10T10:23:42+00:00\" \/>\n<meta property=\"article:modified_time\" content=\"2015-11-12T14:33:14+00:00\" \/>\n<meta property=\"og:image\" content=\"https:\/\/academy.sqlbak.com\/wp-content\/uploads\/2015\/11\/Page-structure.png\" \/>\n<meta name=\"author\" content=\"Alexandr Omelchenko\" \/>\n<meta name=\"twitter:card\" content=\"summary\" \/>\n<meta name=\"twitter:label1\" content=\"Written by\" \/>\n\t<meta name=\"twitter:data1\" content=\"Alexandr Omelchenko\" \/>\n\t<meta name=\"twitter:label2\" content=\"Est. reading time\" \/>\n\t<meta name=\"twitter:data2\" content=\"1 minute\" \/>\n<script type=\"application\/ld+json\" class=\"yoast-schema-graph\">{\"@context\":\"https:\/\/schema.org\",\"@graph\":[{\"@type\":\"WebPage\",\"@id\":\"https:\/\/academy.sqlbak.com\/database-page\/\",\"url\":\"https:\/\/academy.sqlbak.com\/database-page\/\",\"name\":\"Database Page - 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