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6 Replies Latest reply: May 14, 2013 9:41 AM by marksmithusa RSS

Using ACFS as an archive log destination?

marksmithusa Journeyer
Currently Being Moderated
Possibly a bit of a hair-brain idea, but...

I have my ACFS diskgroup set up for both my V1 and V2 systems. We don't use it for anything because we have a batch server connected to the IB fabric which we run everything (batch jobs, etc) from. No need to use ACFS for export files or external tables...

On V2, it's SYSTEMDG and it's got a total usable free space of 288Gb
On V1, it's DBFS_DG and it's got a total usable free space of 858Gb

We have our archivelogs going to the Fast Recovery Area. Obviously, we take great to care the usage of this diskgroup and we have various jobs/scripts which trigger if we hit a certain usage threshold and kick off an archivelog backup (with a delete).

If I wanted to configure Flashback Database, the Flashback logs have to go into the Fast Recovery Area, according to the documentation. If I enable Flashback Database, the Flashback logs won't delete themselves until they're required to do so, which might prove tricky for our script as the FRA will always be '100% full'

We could, I suppose, change the script to calculate the size of the archivelogs only and use that as a trigger and, no doubt, that's by far the easiest way, but I wondered whether anyone had use ACFS for housing the archivelogs.

I believe that you can put 'almost anything' in the ACFS except 'any Oracle files that can be stored in ASM' - presumably this means archivelogs cannot use ACFS.

Has anyone tried such a thing? It seems like a big waste of a decent amount of space to me.

Mark
  • 1. Re: Using ACFS as an archive log destination?
    andy.colvin Oracle ACE
    Currently Being Moderated
    ACFS isn't supported on Exadata - partly, it has to do with the lack of physical devices on the compute nodes. For more info, see MOS note #1326938.1.
  • 2. Re: Using ACFS as an archive log destination?
    marksmithusa Journeyer
    Currently Being Moderated
    That's interesting, because when Oracle came and installed the two machines (a year apart), they allocated space for this.

    However, on reading the MOS note, it's possible that I could have been confusing ACFS with DBFS. Is my suggestion feasible on DBFS?
  • 3. Re: Using ACFS as an archive log destination?
    UweHesse Expert
    Currently Being Moderated
    Andy is correct: ACFS is not supported on Exadata; instead DBFS is.
    This is why in recent deployments the 3rd small diskgroup is called DBFS_DG, by the way.
    However, in your case, you would neither need ACFS nor DBFS.

    You can store archivelogs directly on an ASM diskgroup - no Filesystem needed for that:
    http://docs.oracle.com/cd/E11882_01/server.112/e18951/asmbysql.htm#i1025971
    Typically, that diskgroup is also the Recovery Area, but that is not necessarily so.

    Kind regards
    Uwe Hesse

    "Don't believe it, test it!"
    http://uhesse.com
  • 4. Re: Using ACFS as an archive log destination?
    marksmithusa Journeyer
    Currently Being Moderated
    Uwe Hesse wrote:
    Typically, that diskgroup is also the Recovery Area, but that is not necessarily so.
    That's a good point. Right now, I have the three diskgroups which were configured by Oracle: DATA, FRA, DBFS_DG. I guess I could create another diskgroup, but I'd have to rob space from one of the existing ones and I presume this would mean a resizing of the grid disks, etc. However, once I did that, I could have DATA, FRA, ARCHIVE and DBFS_DG diskgroups - I could put the Flashback Logs into the FRA, archivelogs into the ARCHIVE and continue to not use DBFS_DG.

    We're in the process of trying to persuade management for the virtues of upgrading our Exadata hardware. Should that happen, when Oracle come on-site, they should be able to create a very small DBFS_DG diskgroup and we can split the rest of the space appropriately.

    However, let's say for the sake of argument, that I wasn't allowed to perform the work to create a new diskgroup on my existing system: could I put the archivelogs on DBFS_DG?
  • 5. Re: Using ACFS as an archive log destination?
    Dan.Norris Employee ACE
    Currently Being Moderated
    marksmithusa wrote:
    >

    However, let's say for the sake of argument, that I wasn't allowed to perform the work to create a new diskgroup on my existing system: could I put the archivelogs on DBFS_DG?
    Sure, so long as DBFS_DG has the redundancy level you require (i.e. NORMAL).
  • 6. Re: Using ACFS as an archive log destination?
    marksmithusa Journeyer
    Currently Being Moderated
    Hmm. Very interesting. Although I'm rather hoping we get these new machines so I don't have to worry about it. Something interesting to test, though...

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