Online Backup

[stevenriz]

We are thinking of installing Bakbone's Oracle Online APM for our 10g database. Does anyone have any experience with this APM? It looks to me like you don't need any other Oracle modules in order to get this to work. It looks like this APM puts the DB in Archive Log mode. What exactly is this and how does it work? I am still a little cautious about it. Thanks!
Steve

 

[SantaMufasa]

Steven,

Although I am not familiar with Bakbone's products, any vendor that is worth its salt should be happy to give you references whom you can contact for insight. Additionally, there are 3,430 hits on Google when the search terms are "Bakbone Oracle APM", many of which look like they are objective, third-party assessments.

As far as ARCHIVELOG mode is concerned, this is an extremely important topic for any organisation that cannot afford to lose even one committed transaction, which includes every fiduciary organisation (such as banks or any other money-related institution) and any other processing environment where losing a transaction is not an option.

ARCHIVELOG mode is the feature that allows a DBA to recover a database from the last full backup (either on-line/hot or off-line/cold) and bring the database right back to the most-recently committed transaction.

I won't take the time/space to explain how it works here unless I know that you want that type of input. There are many fine on-line and hardcopy references that explain fully how ARCHIVELOG mode works.

Let us know if this information helps to resolve your needs.

Mufasa
(aka Dave of Sandy, Utah, USA)

http://www.dasages.com

Do you use Oracle and live or work in Utah, USA?
Then click here to join Utah Oracle Users Group on Tek-Tips.

 

[stevenriz]

Thanks Mufasa!! I will learn what Archive Log Mode really means... Of course you are more then welcome to explain but don't go out of your way. I appreciate the insight. I guess I also need to know if this is the preferred, or even an acceptable method of performing an online backup...
thanks!
Steve

 

[SantaMufasa]

I also need to know if this is the preferred, or even an acceptable method of performing an online backup...

Before I say, "Yes it is," please confirm what you mean by "this".


Mufasa
(aka Dave of Sandy, Utah, USA)

http://www.dasages.com

Do you use Oracle and live or work in Utah, USA?
Then click here to join Utah Oracle Users Group on Tek-Tips.

 

[stevenriz]

Oh, Is this the or a preferred method of backing up an Oracle 10g database without shutting it down?

 

[SantaMufasa]

Regardless of whether you use BakBone, some other package, or just-plain Oracle command-line, the only way (of which I am aware) to backup any Oracle "database without stutting it down" is using Oracle's hot-backup capability. Using any other method of backing up while Oracle is "up-and-running" produces a spurious (read: "unusable") backup.

Mufasa
(aka Dave of Sandy, Utah, USA)

http://www.dasages.com

Do you use Oracle and live or work in Utah, USA?
Then click here to join Utah Oracle Users Group on Tek-Tips.

 

[DBAwhosaysNIE]

Oracle works very much like its own journaling filesystem (Reiser, ext3, etc.). archived logs are essentially backup copies of old journals. in simple terms an Oracle hot backup is a copy of the datafiles (or dd of raw devices, etc.) taken after telling Oracle you are about to copy them (alter tablespace system begin backup. when you put tablespace(s) in backup mode Oracle notes the log sequence and SCN (I believe in the controlfile). you (or your tool) then copies the datafiles which are simutaneously being written to (by dbrw). if you ever need to restore from the hot backup Oracle knows it needs to check/synchonize any blocks that were written during the time the tablespace(s) were in backup mode and uses the archived log files to do that.

hot backups are surprisingly simple if you understand Oracle's basic architecture. I do it all with shell scripts (including synching hot standbys) but plently of companys will be happy to take your $$$ for cute GUIs. I'd happily take consulting $$$ but my company has one of those "no moonlighting" policies (that and they already pay me well and keep me more than busy for it)

 

[SantaMufasa]

And one slight extra bit of information to add to DBAwhosaysNIE's excellent overview: When you put a tablespace into "BEGIN BACKUP" mode, not only does "Oracle note the log sequence and SCN," but Oracle also does an additional fascinating thing...it triggers "block-mode redo", meaning that once a tablespace goes into "BEGIN BACKUP" mode, from that moment on, if you UPDATE or DELETE a row, then instead of copying just the old image of the row data, Oracle copies the entire BLOCK in which the row resides. It just needs to do this "full-block" redo write once per block (even if another DML changes a row in the block later). This occurs so that if changes occur during the tablespace backup, if Oracle ever needs to do a RECOVER DATABASE with these backups, it starts with a completely pristine block for the recovery, then it just applies the normal redo entries to the block (which could have been "fractured" i.e, written to during the backup).

Perhaps this is more than you (or anyone) wanted to know, but at least I feel better now.

Mufasa
(aka Dave of Sandy, Utah, USA)

http://www.dasages.com

Do you use Oracle and live or work in Utah, USA?
Then click here to join Utah Oracle Users Group on Tek-Tips.