Re: How are you backing up your V,VLDB????

> Just wondering if partitioning the data on some geographic/spatial
> coordinate basis will help then (presumably mount rushmore isn't moving too
> fast :( ). Whilst this won't get you read only tablespaces it might get you
> logical units of backup that can be backed up in parallel to multiple
> drives?

Partitioning the data like you suggest is a possibility. But it does bring up one other thing that I didn't mention and that is that they layers are "pyramided". We have users view the data on the web. It would really suck to have to read the entire data for the entire US before presenting it to the client's web browser. So we back up a little and take a smaller snapshot of the entire US. Then, we back up again and take an even smaller snapshot. I believe that we create a pyramid of the layer that is 3 or 4 levels high. When you are looking at the entire US, you don't need to as much detail, so we don't give you all of that detail. Then, as you zoom in, you are actually presented with data from the next level of the pyramid. This keeps on until you've reached the lowest level, which has the highest amount of detail.

To facilitate all of this, we are using ESRI's ArcSDE (Spatial Database Engine). ArcSDE handles all of the spatial data for us. (As an aside, it can work in conjunction with Oracle Spatial, or without it.) So when we update the elevation data, we have to redo the pyramids. Unfortunately, pyramiding is an all or nothing proposition. This means to update the elevation data to signify that one entire hill was levelled, we have to pyramid the entire US all over again. This process does take about 20 hours. So as you can see, just having one or two pixels of data changing forces us to change basically the entire layer of pyramids built on top of it.

We do have a cooperative research agreement with ESRI and we are working on "partial-pyramiding", where we don't have to rebuild all of the pyramids when just a few datapoints change. But that technology is still in the future. Until ArcSDE supports partial pyramiding, we won't be able to put part of a spatial layer in READ ONLY mode.

We can however back up in parallel streams. We have an automated tape library system with multiple drives. And RMAN can back up to those drives in parallel. So far, I haven't set it up, but I am looking at that avenue already. When set up, I can back up mutliple tablespaces in unison. I just haven't gotten that far yet.

And it's funny that you mentioned Mount Rushmore as I'm in the state of South Dakota. But on the other side of the state!

Cheers,
Brian Received on Thu Jan 30 2003 - 12:52:57 CST