{"id":615,"date":"2014-08-19T15:48:00","date_gmt":"2014-08-19T15:48:00","guid":{"rendered":"http:\/\/tomvanmaanen.nl\/?p=615"},"modified":"2014-08-19T15:48:00","modified_gmt":"2014-08-19T15:48:00","slug":"teradata-and-fall-back","status":"publish","type":"post","link":"http:\/\/archief.van-maanen.com\/?p=615","title":{"rendered":"Teradata and fall back"},"content":{"rendered":"<p>I understand Teradata has a so-called fall back option. The idea is that data are stored twice; each record being stored to two different amps.<\/p>\n<p>I saw a nice picture that descibes the situation. Each record (Row 1, Row 2 etc) are linked to an amp. It is shown in below scheme as yellow boxes. A seperate copy is made of all records. The copy is shown in an orange box. The records are all linked to another amp as the original record.<\/p>\n<p><a href=\"http:\/\/tomvanmaanen.nl\/wp-content\/uploads\/2014\/08\/TERADATA_FALLBACK.png\"><img loading=\"lazy\" decoding=\"async\" class=\"alignnone size-medium wp-image-616\" src=\"http:\/\/tomvanmaanen.nl\/wp-content\/uploads\/2014\/08\/TERADATA_FALLBACK-300x263.png\" alt=\"TERADATA_FALLBACK\" width=\"300\" height=\"263\" \/><\/a><\/p>\n<p>Having a fall back, certainly has advantages. If an amp fails, a query may use copies of the original records.<\/p>\n<p>However, there is a flipside to this. It requires:<\/p>\n<ul>\n<li>more table space as copies must be stored<\/li>\n<li>more IO time as the copies must be written to disc<\/li>\n<li>more CPU time as he copies must be created by the system<\/li>\n<\/ul>\n<p>Hence, this option is only used for critical tables where the additional costs are justified. Moreover, this option is advised to be used at table level only. This allows to make a fine distinction between tables for whih such additional costs are warrented and other tables where additional costs are not justified.<\/p>\n<p>&nbsp;<\/p>\n","protected":false},"excerpt":{"rendered":"<p>I understand Teradata has a so-called fall back option. The idea is that data are stored twice; each record being stored to two different amps. I saw a nice picture that descibes the situation. Each record (Row 1, Row 2 etc) are linked to an amp. It is shown in below scheme as yellow boxes. [&hellip;]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[5],"tags":[],"class_list":["post-615","post","type-post","status-publish","format-standard","hentry","category-nice-to-know"],"_links":{"self":[{"href":"http:\/\/archief.van-maanen.com\/index.php?rest_route=\/wp\/v2\/posts\/615","targetHints":{"allow":["GET"]}}],"collection":[{"href":"http:\/\/archief.van-maanen.com\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"http:\/\/archief.van-maanen.com\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"http:\/\/archief.van-maanen.com\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"http:\/\/archief.van-maanen.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=615"}],"version-history":[{"count":0,"href":"http:\/\/archief.van-maanen.com\/index.php?rest_route=\/wp\/v2\/posts\/615\/revisions"}],"wp:attachment":[{"href":"http:\/\/archief.van-maanen.com\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=615"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"http:\/\/archief.van-maanen.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=615"},{"taxonomy":"post_tag","embeddable":true,"href":"http:\/\/archief.van-maanen.com\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=615"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}