Kevin, Thanks for your reply.

1) patch up. Some SIGNIFCANT fixes have been put out there for dbcc checkdb recently

This is not a new sql server. It has been running...

I modified the link to make it viewable. Hopefully you can see it now. Thanks.

The CPU doesn't stay at high utilization. It spikes when queries are running. I set the Max Memory as 12 GB out of 16 GB. The task manager shows...

Jeff, the compilation Time is on 6/13. Thank you.

Jeff, The Compilation Time is from the last time the sql server were rebooted. Thanks.

One of the queries comes in on the top in both reports (top queries by total IO and CPU).

It has a total of 1,135,492.95 ms of total CPU time....

Jeff, should I run the report of Top queries by total or average cpu/IO?

Thanks.

It is MEMOBJ_INDEXSTATSMGR that consumes the most memory. I don't find much information about it. Can you help direct me to find the related resource? Thanks

When I ran DBCC memorystatus, MEMORYCLERK_SQLOPTIMIZER consumes about 35.5 GB of memory out of 64 GB total memory. Does it mean I have too many adhoc queries?

Yes, on the sql default trace file, I see a lot of hash and sort operations. How should I solve it? Yes, the PLE seems to be low too. The...

Thank you, Gail. I will look for external memory pressure.

Thank you, Gail, here is the result for select @@version,

Microsoft SQL Server 2008 (SP1) - 10.0.2531.0 (X64)     

Mar 29 2009 10:11:52    

...

From the perfmon, SQLServer:Memory Manager/Total ServerMemory shows 21GB of memory in use, that's what I set the maximum to. I don't where the rest of memory go.

here is part of dbcc memorystatus result, Thanks.

Memory Manager ...

No, it is 64-bit.