{"id":978,"date":"2005-04-25T12:00:00","date_gmt":"2005-04-25T12:00:00","guid":{"rendered":"http:\/\/orcldoug.com\/blog\/?p=978"},"modified":"2005-04-25T12:00:00","modified_gmt":"2005-04-25T12:00:00","slug":"and-theres-more-smu-again","status":"publish","type":"post","link":"http:\/\/orcldoug.com\/blog\/2005\/04\/25\/and-theres-more-smu-again\/","title":{"rendered":"And there’s more … (SMU again)"},"content":{"rendered":"

Almost immediately after posting my last comment on SMU, I noticed that the TAR for the original corruption issue has been updated with a root cause<\/p>\n

Oracle Development has found the root cause of the corruption problem which crippled your database. They have reproduced the problem on an in-house database, thereby confirming the problem and getting the identical results as you experienced on your database. The problem occurs when an undo segment is being transitioned from an ‘offline’ status to an ‘online’ status by a foreground process while the SMON process is doing its regular undo segment maintenance. A small timing window exists when the foreground process releases the latch covering the undo segment and SMON picks up that undo segment and changes the undo segment’s status to ‘invalid’ and releases its space. The foreground process reacquires the latch without rechecking the undo segment’s status field.This problem is fixed in 9.2.0.5 as that piece of code was rewritten to eliminate the timing window.<\/p><\/blockquote>\n

<\/i>Fascinating stuff. I’m pleased that Oracle development have been able to confirm what happened to us, otherwise it might have seemed as though I was crying wolf. The lesson is to be wary of SMU if your server version < 9.2.0.5<\/p>\n","protected":false},"excerpt":{"rendered":"

Almost immediately after posting my last comment on SMU, I noticed that the TAR for the original corruption issue has been updated with a root cause Oracle Development has found the root cause of the corruption problem which crippled your database. They have reproduced the problem on an in-house database, thereby confirming the problem and… Continue reading And there’s more … (SMU again)<\/span><\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[1],"tags":[],"class_list":["post-978","post","type-post","status-publish","format-standard","hentry","category-uncategorized","entry"],"jetpack_featured_media_url":"","jetpack-related-posts":[{"id":979,"url":"http:\/\/orcldoug.com\/blog\/2005\/04\/25\/more-on-system-managed-undo\/","url_meta":{"origin":978,"position":0},"title":"More on System Managed Undo","date":"April 25, 2005","format":false,"excerpt":"In an earlier blog entry, I mentioned that we'd run into pretty severe undo segment corruption problems using SMU on a high-throughput database. Whilst looking for something else on Metalink, I noticed Note 301432.1 which says SymptomsSevere database performance slowdown.(Text snipped out here)CauseLarge numbers of Undo Segment onlines are being\u2026","rel":"","context":"Similar post","img":{"alt_text":"","src":"","width":0,"height":0},"classes":[]},{"id":982,"url":"http:\/\/orcldoug.com\/blog\/2005\/03\/23\/system-managed-undo-problem\/","url_meta":{"origin":978,"position":1},"title":"System Managed Undo Problem","date":"March 23, 2005","format":false,"excerpt":"Tired of trying to fix my daughter's PC (that nightmare's still ongoing) and dealing with the complex emotions of Oracle professionals (that'll be me then), I thought I'd try to post something potentially useful.We use System Managed Undo (or Automatic Undo Management - your choice) on a large number of\u2026","rel":"","context":"Similar post","img":{"alt_text":"","src":"","width":0,"height":0},"classes":[]},{"id":1284,"url":"http:\/\/orcldoug.com\/blog\/2007\/06\/10\/non-reusable-space\/","url_meta":{"origin":978,"position":2},"title":"Non-reusable Space?","date":"June 10, 2007","format":false,"excerpt":"A problem cropped up at work this week and, whilst it wasn't particularly tricky and didn't take long to solve, it struck me that the story of tracking it down might be useful and you might hit the problem yourself one day.A recently-deployed Data Warehouse database at work has a\u2026","rel":"","context":"With 13 comments","img":{"alt_text":"","src":"","width":0,"height":0},"classes":[]},{"id":866,"url":"http:\/\/orcldoug.com\/blog\/2006\/02\/08\/updates\/","url_meta":{"origin":978,"position":3},"title":"Updates","date":"February 8, 2006","format":false,"excerpt":"Just a couple of small updates on some previous blogs.The database that was suffering from network latency problems between it and the app servers was moved down South last week. It all went very smoothly and that particular problem has been resolved. The 20+ hour job runs over night very\u2026","rel":"","context":"Similar post","img":{"alt_text":"","src":"","width":0,"height":0},"classes":[]},{"id":1337,"url":"http:\/\/orcldoug.com\/blog\/2007\/11\/04\/the-reality-gap-2-disaster-recovery\/","url_meta":{"origin":978,"position":4},"title":"The Reality Gap (2) – Disaster Recovery","date":"November 4, 2007","format":false,"excerpt":"I'm going to keep this one short and sweet because I've talked about it before. Because it's based around a single shared database, RAC will not (and was never designed to) protect you from Database corruption Erroneous updates or deletes by a user (or DBA!) More to the point, all\u2026","rel":"","context":"With 16 comments","img":{"alt_text":"","src":"","width":0,"height":0},"classes":[]},{"id":868,"url":"http:\/\/orcldoug.com\/blog\/2006\/02\/05\/we-never-learn-do-we\/","url_meta":{"origin":978,"position":5},"title":"We Never Learn, Do We?","date":"February 5, 2006","format":false,"excerpt":"I had an interesting day at work yesterday. We've run into major performance problems when upgrading a number of Production databases from 8i to 9i. How could that happen, when we've performed regression tests to ensure that the applications perform as well as or better than they did on 8i?Probably\u2026","rel":"","context":"With 5 comments","img":{"alt_text":"","src":"","width":0,"height":0},"classes":[]}],"_links":{"self":[{"href":"http:\/\/orcldoug.com\/blog\/wp-json\/wp\/v2\/posts\/978","targetHints":{"allow":["GET"]}}],"collection":[{"href":"http:\/\/orcldoug.com\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"http:\/\/orcldoug.com\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"http:\/\/orcldoug.com\/blog\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"http:\/\/orcldoug.com\/blog\/wp-json\/wp\/v2\/comments?post=978"}],"version-history":[{"count":0,"href":"http:\/\/orcldoug.com\/blog\/wp-json\/wp\/v2\/posts\/978\/revisions"}],"wp:attachment":[{"href":"http:\/\/orcldoug.com\/blog\/wp-json\/wp\/v2\/media?parent=978"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"http:\/\/orcldoug.com\/blog\/wp-json\/wp\/v2\/categories?post=978"},{"taxonomy":"post_tag","embeddable":true,"href":"http:\/\/orcldoug.com\/blog\/wp-json\/wp\/v2\/tags?post=978"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}