How to create your own Oracle database merge patch

Originally posted on “Databases at CERN” blog

A little bit scary title, isn’t it? Please keep in mind that definitely it is neither supported nor advised method to solve your problems and you should be really careful while doing it – hopefully not on production environment. But it may sometimes happen that you end up with the situation where creating your own merge patch for Oracle database could not be as crazy idea as it sounds :).

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Oracle 12c – causing problem by solving it!?!

Originally posted on “Databases at CERN” blog

Regular readers of our blog probably already know that for most of our databases we’re using two storage layers to keep our backups – NAS volumes as a primary layer and tapes as secondary one – please check Datafile without backups – how to restore? for more details.

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Nuances of Oracle Managed Files (OMF) and RMAN

Originally posted on “Databases at CERN” blog

Oracle Managed Files (OMF) have many advantages, but the fact that such files could coexist in the same database with manually added (and named) ones, could sometimes lead to confusion. Situation is made worse by the fact, that there is no straightforward way (at least of which I’m aware of…or rather was – please check the comment of Mikhail Velikikh visible on CERN’s blog) to say if the file is Oracle managed or not. Oracle documentation seems to confirm this:

The database identifies an Oracle managed file based on its name.

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Which shared memory segments belong to my database instance?

Originally posted on “Databases at CERN” blog

I’ve already described how important is to test your backup strategy and restore/recovery procedures, but while doing so, you could of course encounter some problems, not really related with the recoverability as such. Recently, we’ve got such a problem on our recovery server, at the very beginning of an automatic restore (database name masked):

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Potential of “import catalog” command

Originally posted on “Databases at CERN” blog

Since version 11.1 of Oracle database, there is very useful command available, allowing DBAs to easily move RMAN recovery catalog schemas between databases. Its functionality is even broader, as it also allows one catalog schema to be merged into another – either the whole schema or just the metadata of chosen databases. Command I’m writing about is of course IMPORT CATALOG, which I had a chance to use recently, to move our recovery catalog to the new database. It was moved from Oracle 11.2.0.3 database to 11.2.0.4, with recovery catalog schema using below version:

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Datafile without backups – how to restore?

Originally posted on “Databases at CERN” blog

Have you ever had a problem with restoring datafiles without any backups available? It’s easy, of course if you have all archived logs from the time datafile was created. Please check it here: Re-Creating Data Files When Backups Are Unavailable. Moreover, RMAN is clever enough to create empty datafile automatically during restore phase and then recover it using archived logs. So far, so good, but…

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Importance of testing yours backup strategy

Originally posted on “Databases at CERN” blog

Most of you for sure know, that ability to restore data in case of failure is a primary skill for each DBA. You should always be able to restore and recover data you’re responsible for. This is an axiom. To be sure, that you’re able to do it, you should test it on regular basis. There is of course possibility to use some Oracle features, like BACKUP ... VALIDATE or RESTORE ... VALIDATE commands, but if you want to be certain as much as possible, the only way is just to run real restore and recovery. Doing it periodically for big amount of databases is extremely tough, both because of resources needed and DBA time. That’s why one of our DBAs Ruben Gaspar Aparicio has created recovery system, which is heavily used at CERN. Good news – it is available as Open Source on Sourceforge (Recovery Platform). Since its release we’ve introduced many modifications to it, but still it could be good starting point to check the source code in order to start developing your own solution. We’re using it as a validation of our backup strategy, to run real restore and recovery every week or two for most of our databases.

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