Re: Re: HCC in Pillar Storage
Date: Tue, 20 Mar 2012 19:56:15 +0000
I wouldn't do that :)
But if any of the datafiles in a tablespace are outside HCC-supported storage, then the entire tablespace will become not supported for HCC (nor smart scanning).
So watch out before adding NFS-based datafiles into your existing storage cell based tablespaces, you will suddenly start getting these errors when trying to access any HCC compressed data:
*ORA-64307: hybrid columnar compression is not supported for tablespaces on this storage type*
... and the smart scans are disabled for the entire tablespace.
Starting from 11g, you can actually drop individual datafiles of a tablespace (if they are empty), so once you drop the non-compatible file, everything will be back to normal.
-- *Tanel Poder* Enkitec Europe +372 56 956 181 http://www.enkitec.com/ Expert Oracle Exadata book: http://www.apress.com/9781430233923 On Tue, Mar 20, 2012 at 5:46 PM, Ls Cheng <exriscer_at_gmail.com> wrote:Received on Tue Mar 20 2012 - 14:56:15 CDT
> Thanks for the explanation
> So if a tablespace has 2 datafiles, one per array, and if a segment
> located in the tablespace spans in these two datafiles, can this segment
> have part of data in HCC and others parts not?
> On Tue, Mar 20, 2012 at 6:29 PM, Tanel Poder <tanel_at_tanelpoder.com> wrote:
>> Oracle supports HCC on Exadata and from 184.108.40.206 onwards on Oracle's (Sum)
>> ZFS appliance and Pillar. Obviously on non-Exadata the *de*compression
>> always happens at the database layer (on Exadata it depends on a number of
>> things). The compression always happens in the database layer on both
>> Exadata and non-Exadata.
>> The HCC "support" is decided at the tablespace level, but HCC itself is
>> enabled at the segment level. So you can have a table residing in
>> HCC-capable tablespace, but you decide not to compress it.
>> This segment-level approach also means that you can move the oldest
>> partitions of a partitioned fact table onto Pillar/ZFS appliance (and keep
>> it compressed with HCC if you want) while keeping the newest partitions of
>> the same table on Exadata storage. By the way, even with regular NFS
>> appliances or iSCSI storage you can keep some partitions of a table off
>> Exadata (without HCC) while keeping other partitions on Exadata.
>> *Tanel Poder*
>> Enkitec Europe
>> +372 56 956 181
>> Expert Oracle Exadata book:
>> On Tue, Mar 20, 2012 at 4:13 PM, Vit Spinka <vit.spinka_at_vitspinka.cz>
>> > The HCC is usually done by the storage; if the storage decides not to do
>> > so (e.g. due to CPU load), it will pass the blocks uncompressed and it's
>> > then job of the database to uncompress them. So Oracle does not support
>> > HCC on non-Exadata/Pillar, but it could do so, but with performance hit.
>> > >> I am wondering because I am not very sure where is HCC done, if it
>> > done
>> > >> in the DB how the hcc algorithm applies for some blocks (pillar) and
>> > some
>> > >> not (EVA), if it works shouldnt be a performance hit?
>> > >>
>> > >
>> > --
>> > http://www.freelists.org/webpage/oracle-l