{"id":5469,"date":"2015-09-06T17:11:37","date_gmt":"2015-09-06T15:11:37","guid":{"rendered":"https:\/\/www.dbi-services.com\/blog\/set-stateapply-off-and-datafile-consistency\/"},"modified":"2015-09-06T17:11:37","modified_gmt":"2015-09-06T15:11:37","slug":"set-stateapply-off-and-datafile-consistency","status":"publish","type":"post","link":"https:\/\/www.dbi-services.com\/blog\/set-stateapply-off-and-datafile-consistency\/","title":{"rendered":"set state=apply-off and datafile consistency"},"content":{"rendered":"

By Franck Pachot<\/h2>\n

.
\nIn a standby database (or in any database you recover) do you think the recovery uses buffer cache? And when you stop the apply in a standby database, do you think the datafiles are in a consistent state? We know the answer, but want to prove it. This is the kind of question you may have, as I did last Friday morning in the train with Ludovico Caldara<\/a> when going to the Paris Oracle Meetup<\/a>.
\n
\nHere is the buffer cache status summary in a Data Guard standby database instance:<\/p>\n

\nSQL> select status,count(*) from v$bh group by status;\n \nSTATUS       COUNT(*)\n---------- ----------\nfree             1473\nmemory              2\nmrec             4846\n<\/code><\/pre>\n
The MREC status is the status of the blocks where redo from recovery is applied. It’s a current version of the block for recovery purpose only.<\/p>\n
Let’s see what happens when we stop the apply:<\/p>\n
\nDGMGRL> edit database demo12 set state=apply-off;\nSucceeded.\n<\/code><\/pre>\n
The alert.log shows that the data files are in a consistent state, which is similar to a checkpoint:<\/p>\n
\nRecovery interrupted!\nRecovered data files to a consistent state at change 5683001\n<\/code><\/pre>\n
And here is the buffer cache:<\/p>\n
\nSQL> select status,count(*) from v$bh group by status;\n \nSTATUS       COUNT(*)\n---------- ----------\nfree             6344\n<\/code><\/pre>\n
All my MREC blocks have become free, as with any checkpoint.<\/p>\n
It’s exactly what we expected, but sometimes I just want to prove it to myself because there can be bugs, implementation oddities, or simply something that I overlooked. Now I’m conviced: the physical standby data files are consistent after an apply-off.<\/p>\n","protected":false},"excerpt":{"rendered":"
By Franck Pachot . In a standby database (or in any database you recover) do you think the recovery uses buffer cache? And when you stop the apply in a standby database, do you think the datafiles are in a consistent state? We know the answer, but want to prove it. This is the kind […]<\/p>\n","protected":false},"author":27,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"footnotes":""},"categories":[229,59],"tags":[638,639,221,96],"type_dbi":[],"class_list":["post-5469","post","type-post","status-publish","format-standard","hentry","category-database-administration-monitoring","category-oracle","tag-apply-off","tag-checkpoint","tag-data-guard","tag-oracle"],"acf":[],"yoast_head":"\nset state=apply-off and datafile consistency - dbi Blog<\/title>\n<meta name=\"description\" content=\"checkpoint at apply-off\" \/>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" href=\"https:\/\/www.dbi-services.com\/blog\/set-stateapply-off-and-datafile-consistency\/\" \/>\n<meta property=\"og:locale\" content=\"en_US\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"set state=apply-off and datafile consistency\" \/>\n<meta property=\"og:description\" content=\"checkpoint at apply-off\" \/>\n<meta property=\"og:url\" content=\"https:\/\/www.dbi-services.com\/blog\/set-stateapply-off-and-datafile-consistency\/\" \/>\n<meta property=\"og:site_name\" content=\"dbi Blog\" \/>\n<meta property=\"article:published_time\" content=\"2015-09-06T15:11:37+00:00\" \/>\n<meta name=\"author\" content=\"Oracle Team\" \/>\n<meta name=\"twitter:card\" content=\"summary_large_image\" \/>\n<meta name=\"twitter:label1\" content=\"Written by\" \/>\n\t<meta name=\"twitter:data1\" content=\"Oracle Team\" \/>\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\":\"Article\",\"@id\":\"https:\/\/www.dbi-services.com\/blog\/set-stateapply-off-and-datafile-consistency\/#article\",\"isPartOf\":{\"@id\":\"https:\/\/www.dbi-services.com\/blog\/set-stateapply-off-and-datafile-consistency\/\"},\"author\":{\"name\":\"Oracle Team\",\"@id\":\"https:\/\/www.dbi-services.com\/blog\/#\/schema\/person\/66ab87129f2d357f09971bc7936a77ee\"},\"headline\":\"set state=apply-off and datafile consistency\",\"datePublished\":\"2015-09-06T15:11:37+00:00\",\"mainEntityOfPage\":{\"@id\":\"https:\/\/www.dbi-services.com\/blog\/set-stateapply-off-and-datafile-consistency\/\"},\"wordCount\":214,\"commentCount\":0,\"keywords\":[\"apply-off\",\"checkpoint\",\"Data Guard\",\"Oracle\"],\"articleSection\":[\"Database Administration & Monitoring\",\"Oracle\"],\"inLanguage\":\"en-US\",\"potentialAction\":[{\"@type\":\"CommentAction\",\"name\":\"Comment\",\"target\":[\"https:\/\/www.dbi-services.com\/blog\/set-stateapply-off-and-datafile-consistency\/#respond\"]}]},{\"@type\":\"WebPage\",\"@id\":\"https:\/\/www.dbi-services.com\/blog\/set-stateapply-off-and-datafile-consistency\/\",\"url\":\"https:\/\/www.dbi-services.com\/blog\/set-stateapply-off-and-datafile-consistency\/\",\"name\":\"set state=apply-off and datafile consistency - 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