It's interesting indeed. Why don't you formally log a case with Symantec Tech Support to find out what exactly is happening. I'm sure they could come up with some performance tuning recommendation or would be interested to see the cause of this major performance difference.

Hello.

It looks like expected behavior. Here is some assumptions.

Veritas ODM gives to you "like row device performance" with all negatives and positives.

I think your DB is read aggressive, not write (OLAP?).

I think if you will look to yours statspacks you will see significant improvement in write operations. But, I think, your read operations become worse with ODM.

So than you DB works with out of veritas ODM you heavily use file system cache and it helps a lot with read operations. But than you enable veritas ODM you read directly from disk, with out of this case, so service time and amount of read operations go up.

For this type of load ODM isn't the best choice. It can be enabled and be useful, but after rather big DB enhancements.