Posts by Alex Gorbachev

“ORA-1652: Unable To Extend Temp Segment” in RAC

Today I’ve seen a question on OTN forum about ORA-1652 in alert.log in RAC environment. I immediately recalled the bug and thought that I should mention that here. I quickToday I’ve seen a question on OTN forum about ORA-1652 in alert.log in RAC environment. I immediately recalled the bug and thought that I should mention that here. I quickly found Metalink Note 258941.1 and was surprised to see that there are actually two bugs on that and I only was aware of one so I definitely have to blog about it now.ly found Metalink Note 258941.1 and was surprised to see that there are actually two bugs on that and I only was aware of one so I definitely have to blog about it now.

What Happens When You Leave an Oracle Database in Backup Mode

So one fine evening, there was a scheduled maintenance, and one of the databases didn’t shutdown cleanly (thanks to mis-configured Windows services, if I recall correctly). Consequently, the database crashed and later didn’t come back up.When I looked at it in the morning, the error message rang a bell: “Datafile 1 needs media recovery” in combination with the request for very old archivelogs.The moral of the story: do not leave datafiles in backup mode. If you use hot backups outside of RMAN, such as snapshot technologies, take care to implement monitoring so that the database doesn’t stay in backup mode for much time.

Changing Hostnames in Oracle RAC

Sometimes there is a desperate need to change hostnames for one or all nodes of an Oracle RAC cluster. However, this operation is not officially supported. One way to do it is to remove a node from a cluster, change its hostname, and then add it back to the cluster as a new node. If you are brave enough, there is another way to do this. Find out here.

Oracle Coherence vs. Oracle RAC or Coherence + MySQL = MySQL RAC?

I came across Oracle Coherence today. Seems like this is another approach to clustering than Oracle RAC. Seems like this is a way to scale middle tiers that require shared data without actually using the central database for that. On the other hand, looks like a clustering framework with rules defined by developers as opposed to Oracle RAC that is designed and built to be a black box delivering database services. Has anyone (yeah, I’m asking developers reading the blog) played with it and knows how it feels?

MSDBF 07: Final Wrap Up

A few days ago, I did a short post about the start of the Miracle Scotland Database Forum 2007. I decided to wait until getting back home to complete a full-blown description of the event. I should warn you, this will be quite lengthy, so draw a deep breath.

Miracle Scotland Database Forum – Day One

Yesterday was the opening and I should say it was great — nice tour on the Whiskey Heritage Center and couple interesting and humorous sessions delivered by Jonathan Lewis and Graham Wood combined with whiskey tasting. The evening obviously continued after that but you can assume that anyway if you know what I’m talking about.

Block Change Tracking Internals: X$ Tables Research

With this post, I’m starting a series about Oracle Block Change Tracking internals. The feature was introduced in Oracle 10 Release 1. I have already published my past presentations and the white paper about that. When I first started, I tried to dig at least something from Metalink, but the public notes contained no implementation details. What I extracted is some pieces of bug texts, and from there I concluded that fixed tables starting with X$KRC are most probably related to the BCT feature.

21-hours Phantom SELECT Causing ORA-1555 ‘snapshot too old’

One of our clients had an ORA-1555 “snapshot too old” error two nights in a row. The quick and dirty fix would be to increase the retention_period and the potential size of the UNDO tablespace. I was looking at it together with Dave, my new team mate, and a small detail popped up right away — Query Duration=76584 — 21+ hours? I checked the retention period, and it was 2 hours, so the dirty fix would probably fail unless it’s very dirty — dumping undo retention to something like a day and blowing the UNDO tablespace, and still without guarantee that the query finish within a day.

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