Oracle and dbc_max_pct

[Thomas Lee_1]

Jakes Louw

1.Oh, sorry for my lack of PVG, can you have
a brief explain?
Also what intelligent combinations for VG&PVGs can be used?

2.Usually if split mirror to backup, how much time need to sync when merge? My db size around 60G.

[Jakes Louw]

PVG = Physical Volume Group. This is one way to group PVs within a VG, so that you can perform Distributed Striping (have a look at manpages for vgcreate and lvcreate). What we do is to try and make sure that we spread the load by choosing PVs that are on different channels. Of course, the more the channels, the better the performance benefits. When we need to enlarge or extend a VG, we make sure that we enlarge it with a minimum number of disks, or else any striping becomes invalidated. Obviously the minimum is 2 disks for a vgextend, but from experience, we have found that 4 disks is optimum. I have used Distributed Striping with a 80-disk stripe-set with great results. Remember, if you do not have something like PowerPath, you need to make sure that you switch every alternate path over.
Syncing speed: haven't done it in a while, but you only do this after the backup from the mirror is complete. You'll have to test it and find out. I'm not sure if HP uses a track table, or whether they actually flag each track physically, but the sync speed is dependant on the number of updates and the speed of the disks. Just remember that while the mirror is split, you are at risk from corruption on the primary. Recovering from this point would imply a sync back from the mirror, with attendant data loss. Double-check your sync scripts before using on a live system.