Exadata storage cells (starting from cellsrv v126.96.36.199.0 / Jan 2015) can
use fully columnar flash cache for greatly speeding up reads (the cache is
fully columnar, not hybrid like the datafile storage).
You can look into slides 17-20 in this presentation (from 2015), some
things may have changed/improved by now:
This would speed up queries doing lots of scanning *if* your current SQL
performance bottleneck is about reading too many datafile blocks (and not
somewhere else, like having a large fact-fact hash join spill to temp).
This columnar flash caching won't speed up writes & large data loads.
So, if the goal is to speed up your ETL processing, you should first
measure (if you haven't done so already) where the response time of your
ETL jobs is spent... and see if it's in *smart scan data retrieval*, where
the storage cells can't somehow keep up with the data ingest demand of the
DB layer and they waif for disk reads a lot (but I'd say it's unlikely...
depending on how your flash cache allowance is set up. You might already be
benefitting from the columnar flash cache, the slides have metrics that
show how much).
Otherwise, just to reduce I/O (which kind of I/O - data retrieval for scans
or data processing for GROUP BY/HASH JOINs?), you could review your top
SQLs' execution plans and see if a better partitionings, subpartitioning
(and maybe even Exadata-aware indexing) scheme would help to allow doing
less I/O. I would look into fancier things like attribute clustering (and
zone maps) after done with the basics first.
On Tue, Sep 21, 2021 at 2:48 PM Lok P <loknath.73@xxxxxxxxx> wrote:
Hello Listers, We have oracle exadata databases which are performing
mostly warehousing or batch type data processing. And few are hybrid i.e
combination of both oltp+warehousing/analytics types processing. ETL jobs
run on a few of these which move/read/write billions rows daily.
The databases are 50TB to ~150TB in size currently. Few architecture
team members suggested evaluating if we can use columnar database type of
offering for IO reduction and thus better performance considering the
future growth. As per my understanding , Oracle stores data in row format
only, so is there any other offering from Oracle for columnar datastore
format or columnar databases and we should evaluate that? Or is there any
clustering kind of technique which can be evaluated which will help reduce
IO? Want to understand experts' views here on this.