{"id":168,"date":"2018-07-19T05:24:22","date_gmt":"2018-07-19T05:24:22","guid":{"rendered":"http:\/\/csp4.epgpbooks.inflibnet.ac.in\/?post_type=chapter&#038;p=168"},"modified":"2018-07-19T05:25:00","modified_gmt":"2018-07-19T05:25:00","slug":"database-recovery","status":"publish","type":"chapter","link":"https:\/\/ebooks.inflibnet.ac.in\/csp4\/chapter\/database-recovery\/","title":{"rendered":"Database Recovery"},"content":{"raw":"<ul>\r\n \t<li>Process of restoring a database to a correct state in the event of failure.(Or)<\/li>\r\n \t<li>Process of restoring the database to the most recent consistent state that existed shortly before the time of system failure.<\/li>\r\n \t<li>Recovery restores a database from a given state, usually inconsistent to a previously consistent state.<\/li>\r\n \t<li>Number of recovery techniques are based on atomicity properties.<\/li>\r\n \t<li>Generally follows a predictable scenario.<\/li>\r\n \t<li>Determines type and extend of the required recovery.<\/li>\r\n \t<li>If entire database needs to be recovered to a consistent to a consistent state, the recovery uses the most recent backup copy.<\/li>\r\n \t<li>Some DBMS provide functions that allow administrator to schedule automatic backup to secondary storage devices on tapes, CDs, disks etc.,<\/li>\r\n \t<li>Levels of database backup:<\/li>\r\n \t<li>Full backup or dump of a database.<\/li>\r\n \t<li>A differential backup of the database in which only the last modifications done to the database, to the previous copy are copied.<\/li>\r\n \t<li>Backup of transaction log only.<\/li>\r\n \t<li>Hardware failures: includes memory errors, disk crashes, bad disk sectors, disk full errors and so on\u2026 This can attribute to design errors, inadequate quality control during fabrication, overloading and wear-out of mechanical parts.<\/li>\r\n \t<li>Software Failure: failures related to software such as operating system, DBMS software, application programs and so on.<\/li>\r\n \t<li>System Crashes: due to software and hardware errors, resulting in the loss of main memory.<\/li>\r\n \t<li>there could be situation where system can enter deadlock state.<\/li>\r\n \t<li>Network Failures: occur while using client server configuration or distributed database system. Communication failures or aborted synchronous connections will interrupt the normal operation.<\/li>\r\n \t<li>Media Failures: due to head craches or unreadable media, resulting in the loss of parts of secondary storage.<\/li>\r\n \t<li>Application Software Failures: logical errors that cause one or more transactions to fail.<\/li>\r\n \t<li>Natural Physical Disasters: failure like fire, flood, earthquake or power failures.<\/li>\r\n \t<li>Carelessness: un-intentional destruction of data.<\/li>\r\n \t<li>Sabotage: intentional corruption or destruction of data<\/li>\r\n \t<li>Transaction represent basic unit of recovery in a database system.<\/li>\r\n \t<li>Transaction begins with successful execution of &lt;t, BEGIN&gt; statement.<\/li>\r\n \t<li>Ends with successful execution of a COMMIT statement.<\/li>\r\n \t<li>Forward Recovery<\/li>\r\n \t<li>Backward Recovery<\/li>\r\n \t<li>Also called Roll Forward, is used in the case of physical damage or failure during transferring buffers to secondary storage.<\/li>\r\n \t<li>Intermediate transactions are stored in database buffers.<\/li>\r\n<\/ul>\r\n<p style=\"text-align: center\"><img class=\"size-full wp-image-170 aligncenter\" src=\"http:\/\/csp4.epgpbooks.inflibnet.ac.in\/wp-content\/uploads\/sites\/47\/2018\/07\/a2-72.png\" alt=\"\" width=\"636\" height=\"363\" \/><\/p>\r\n&nbsp;","rendered":"<ul>\n<li>Process of restoring a database to a correct state in the event of failure.(Or)<\/li>\n<li>Process of restoring the database to the most recent consistent state that existed shortly before the time of system failure.<\/li>\n<li>Recovery restores a database from a given state, usually inconsistent to a previously consistent state.<\/li>\n<li>Number of recovery techniques are based on atomicity properties.<\/li>\n<li>Generally follows a predictable scenario.<\/li>\n<li>Determines type and extend of the required recovery.<\/li>\n<li>If entire database needs to be recovered to a consistent to a consistent state, the recovery uses the most recent backup copy.<\/li>\n<li>Some DBMS provide functions that allow administrator to schedule automatic backup to secondary storage devices on tapes, CDs, disks etc.,<\/li>\n<li>Levels of database backup:<\/li>\n<li>Full backup or dump of a database.<\/li>\n<li>A differential backup of the database in which only the last modifications done to the database, to the previous copy are copied.<\/li>\n<li>Backup of transaction log only.<\/li>\n<li>Hardware failures: includes memory errors, disk crashes, bad disk sectors, disk full errors and so on\u2026 This can attribute to design errors, inadequate quality control during fabrication, overloading and wear-out of mechanical parts.<\/li>\n<li>Software Failure: failures related to software such as operating system, DBMS software, application programs and so on.<\/li>\n<li>System Crashes: due to software and hardware errors, resulting in the loss of main memory.<\/li>\n<li>there could be situation where system can enter deadlock state.<\/li>\n<li>Network Failures: occur while using client server configuration or distributed database system. Communication failures or aborted synchronous connections will interrupt the normal operation.<\/li>\n<li>Media Failures: due to head craches or unreadable media, resulting in the loss of parts of secondary storage.<\/li>\n<li>Application Software Failures: logical errors that cause one or more transactions to fail.<\/li>\n<li>Natural Physical Disasters: failure like fire, flood, earthquake or power failures.<\/li>\n<li>Carelessness: un-intentional destruction of data.<\/li>\n<li>Sabotage: intentional corruption or destruction of data<\/li>\n<li>Transaction represent basic unit of recovery in a database system.<\/li>\n<li>Transaction begins with successful execution of &lt;t, BEGIN&gt; statement.<\/li>\n<li>Ends with successful execution of a COMMIT statement.<\/li>\n<li>Forward Recovery<\/li>\n<li>Backward Recovery<\/li>\n<li>Also called Roll Forward, is used in the case of physical damage or failure during transferring buffers to secondary storage.<\/li>\n<li>Intermediate transactions are stored in database buffers.<\/li>\n<\/ul>\n<p style=\"text-align: center\"><img loading=\"lazy\" decoding=\"async\" class=\"size-full wp-image-170 aligncenter\" src=\"http:\/\/csp4.epgpbooks.inflibnet.ac.in\/wp-content\/uploads\/sites\/47\/2018\/07\/a2-72.png\" alt=\"\" width=\"636\" height=\"363\" srcset=\"https:\/\/ebooks.inflibnet.ac.in\/csp4\/wp-content\/uploads\/sites\/47\/2018\/07\/a2-72.png 636w, https:\/\/ebooks.inflibnet.ac.in\/csp4\/wp-content\/uploads\/sites\/47\/2018\/07\/a2-72-300x171.png 300w, https:\/\/ebooks.inflibnet.ac.in\/csp4\/wp-content\/uploads\/sites\/47\/2018\/07\/a2-72-65x37.png 65w, https:\/\/ebooks.inflibnet.ac.in\/csp4\/wp-content\/uploads\/sites\/47\/2018\/07\/a2-72-225x128.png 225w, https:\/\/ebooks.inflibnet.ac.in\/csp4\/wp-content\/uploads\/sites\/47\/2018\/07\/a2-72-350x200.png 350w\" sizes=\"auto, (max-width: 636px) 100vw, 636px\" \/><\/p>\n<p>&nbsp;<\/p>\n","protected":false},"author":4,"menu_order":21,"template":"","meta":{"_acf_changed":false,"pb_show_title":"on","pb_short_title":"","pb_subtitle":"","pb_authors":["dr-r-baskaran"],"pb_section_license":""},"chapter-type":[],"contributor":[58],"license":[],"class_list":["post-168","chapter","type-chapter","status-publish","hentry","contributor-dr-r-baskaran"],"part":3,"_links":{"self":[{"href":"https:\/\/ebooks.inflibnet.ac.in\/csp4\/wp-json\/pressbooks\/v2\/chapters\/168","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/ebooks.inflibnet.ac.in\/csp4\/wp-json\/pressbooks\/v2\/chapters"}],"about":[{"href":"https:\/\/ebooks.inflibnet.ac.in\/csp4\/wp-json\/wp\/v2\/types\/chapter"}],"author":[{"embeddable":true,"href":"https:\/\/ebooks.inflibnet.ac.in\/csp4\/wp-json\/wp\/v2\/users\/4"}],"version-history":[{"count":2,"href":"https:\/\/ebooks.inflibnet.ac.in\/csp4\/wp-json\/pressbooks\/v2\/chapters\/168\/revisions"}],"predecessor-version":[{"id":171,"href":"https:\/\/ebooks.inflibnet.ac.in\/csp4\/wp-json\/pressbooks\/v2\/chapters\/168\/revisions\/171"}],"part":[{"href":"https:\/\/ebooks.inflibnet.ac.in\/csp4\/wp-json\/pressbooks\/v2\/parts\/3"}],"metadata":[{"href":"https:\/\/ebooks.inflibnet.ac.in\/csp4\/wp-json\/pressbooks\/v2\/chapters\/168\/metadata\/"}],"wp:attachment":[{"href":"https:\/\/ebooks.inflibnet.ac.in\/csp4\/wp-json\/wp\/v2\/media?parent=168"}],"wp:term":[{"taxonomy":"chapter-type","embeddable":true,"href":"https:\/\/ebooks.inflibnet.ac.in\/csp4\/wp-json\/pressbooks\/v2\/chapter-type?post=168"},{"taxonomy":"contributor","embeddable":true,"href":"https:\/\/ebooks.inflibnet.ac.in\/csp4\/wp-json\/wp\/v2\/contributor?post=168"},{"taxonomy":"license","embeddable":true,"href":"https:\/\/ebooks.inflibnet.ac.in\/csp4\/wp-json\/wp\/v2\/license?post=168"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}