enq: HW - contention

  • From: "Tim Onions" <att755@xxxxxxxxxxx>
  • To: Oracle-L@xxxxxxxxxxxxx
  • Date: Tue, 17 Jan 2006 15:16:22 +0000

10gR2, RHEL4, OCFS2, DL585 AMD Opteron 64bit

Im running a benchmark on the above hardware using hammerora (GPL TPC like tool I saw a presention on at UK OUG 2005). All runs very fast to begin with but then slows to a crawl. AWR/ADDM shows the reason for the slow down to be HWM contention presumably do to a large number of multiple concurrent inserts happening (once the initial HWM is breeched). I did some googling and found lots of references to the _bump_highwatre_mark_count parameter to "fix" this. My question is as I am using ASSM tablspaces surely this no longer applies - there are no freelists/freelist groups on such tablespaces if my understanding is correct. If this is so then why am I getting this contention and how can it be fixed when using ASSM. I will try the parameter next time I hit the issue.

Many thanks

Tim Onions

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