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APPR - asynchronous pages read per request

P: n/a
I used 5 physical disks to form a volumn group in AIX and created a
JFS2 logical volumn on it with maximum "RANGE of physical volumes"
setting. Two tablespace containers, with 8K and 32K pagesize, are put
into the mount point.

Question 1: How to know the stripe size of this AIX VG for setting
EXTENTSIZE?

Anyway I used default setting, 32, for EXTENTSIZE. Since there are
totat 5 disks in the VG, I set the PREFETCHSIZE to 32*5 = 160,
NUM_IOSERVERS = 5 and I suppose each prefetch request can get 160
pages from the tablespace. However, when I issue a full table scan
query on the tables, the APPR for 8K table is 30 and 32K is 15 only.
The value of APPR cannot be increased by increasing the bufferpool
size.

Question 2: Is it normal that the APPR is much smaller than
PREFETCHSIZE?

APPR is calculated by POOL_ASYNC_DATA_READS /
POOL_ASYNC_DATA_READ_REQS from snapshot_bp table.

Thanks.

Apr 3 '07 #1
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