September 2010

One of the simple scripts I use from time to time monitors the amount of undo generated by a long running session by taking a session id (SID) as an input and joining v$session to v$transaction:

column start_scn format 999,999,999,999

select
        tr.start_scn, tr.log_io, tr.phy_io, tr.used_ublk, tr.used_urec, recursive
from
        v$session       se,
        V$transaction   tr
where
        se.sid = &1
and     tr.ses_addr = se.saddr
;

       START_SCN     LOG_IO     PHY_IO  USED_UBLK  USED_UREC REC
---------------- ---------- ---------- ---------- ---------- ---
 136,509,466,121   10730956     358074          1          1 NO
 136,515,115,543         12          0          1          3 YES

You’ll note that this is a session that has been doing quite a lot of work. I was watching it because I wanted to check that it was only generating undo in a series of very short recursive transactions. (It’s running a coalesce on a very large, very smashed, index).

We've just added talks on Exadata and MySQL starting at 1:15-2pm today.

Oracle had the new version of the Exadata Machine on display at Oracle Open World this week. It’s called the Exadata X2-8. That’s a catchy name. It sounds very Iron Manish! In fact they had these fellows on display next to the demo machines.

The X2-8 uses two 4U Sun Fire x4800 servers which each have 8 x eight-core intel CPUs (X7560) and 1 Terabyte of memory along with 14 Exadata Storage Servers. Here’s a link to the spec sheet for the X2-8 and for the Oracle Sun X4800. Below are a couple of pictures. The first one shows one of the database servers (X4800) with one of the CPU modules out.

The storage cells have not changed much from the original V2. They still have 2 CPUs and 12 drives and 384G of flash cache. Although I’ve been told they have newer (faster) 6 core Intel CPUs. (I did get a look at an unpublished spec sheet on an Oracle employee’s iPhone and it said they were using the 5670 CPUs) Oh, and they will allow you to run Solaris on the database servers. Of course they will have to finish a new version of Solaris 11 before that can happen. It’s worth noting that X2-8 can be ordered but that they don’t have a firm delivery date yet.

So this configuration is definitely for the high end market and addresses a couple of issues. The increased memory will allow us to have a more robust consolidation platform. It will also allow bigger OLTP type systems to run better (i.e. the additional memory means we can support many more concurrent users and have much larger buffer caches). Note that Exadata’s offloading generally reduces the memory requirements, but nevertheless, very large systems, particularly ones with lot’s of fast OLTP type transactions and lot’s of users will be better satisfied by this type of configuration. Also note that there is no little brother version of the X2-8. It comes in a full rack only. Which makes sense because there are only two database machines. I don’t believe the price has been set yet, but the word on the street is that the hardware will be about 50% more than the full rack version with the small 2 CPU blades (now renamed X2-2 by the way).

I did a post a couple of weeks ago (Thoughts on Exadata V3) about what I thought we might get to see in the way of Exadata changes. We got most of the things I was expecting but not all of them. Among the things we got are bigger/beefier servers with more memory and available slots for HBAs to provide some additional connection capabilities (although I’m not sure if Oracle is going to want people to open the machines up and put additional controllers in). I did see mention in the x4800 spec sheet of an HBA so they may actually have one in there already (I need to check that out). They also announced that they will be offering a version of Solaris that can run on the database servers which I was expecting, although they are still using Intel chips. The thing I was expecting that didn’t happen was a change of mind set about flexibility of configuration. They seem pretty set on maintaining a fixed configuration that will be the same for every customer. That is probably not such a bad idea. Certainly it’s easier to support and faster to deploy. But you know how customers are, they want their hamburgers with extra mustard and no pickles. So we’ll see how that works out over time. But for now, it’s a fixed menu. To quote Henry Ford, “You can get it in any color you want as long as it’s black”.

So that’s all I can think of at this point. Please let me know if you have any questions and I’ll see what I can find out.

This year I have a presentation titled "Query Transformations" in Moscone South, Room 300 on Thursday, September 23 at 12:00. In last years I had done a similar presentation several times at different conferences. However, this presentation contains new transformations which came in Oracle 11gR2. The list of query transformations I will talk about is the following: