Oracle direct path read IO size
Hello!
I am confused a little with IO size. I am running 11.2.0.3 on Oracle Linux x64 6.2. Block_size=8K, MULTIBOCK_READ_COUNT=128
Database is Single Instance and is using ASM grid. ASM AU =1M
As a test I am running a simple query against large table with 1.5Bln rows.
select /*+ PARALLEL (STOCK_DAY 10) */ count(*) from stock_day where cstast='NA'
STAT #140582923121480 id=1 cnt=0 pid=0 pos=1 obj=0 op='SORT AGGREGATE (cr=0 pr=0 pw=0 time=0 us)'
STAT #140582923121480 id=2 cnt=0 pid=1 pos=1 obj=0 op='PX COORDINATOR (cr=0 pr=0 pw=0 time=0 us)'
STAT #140582923121480 id=3 cnt=0 pid=2 pos=1 obj=0 op='PX SEND QC (RANDOM) :TQ10000 (cr=0 pr=0 pw=0 time=0 us)'
STAT #140582923121480 id=4 cnt=0 pid=3 pos=1 obj=0 op='SORT AGGREGATE (cr=0 pr=0 pw=0 time=27 us)'
STAT #140582923121480 id=5 cnt=2301843 pid=4 pos=1 obj=0 op='PX PARTITION LIST ALL PARTITION: 1 762 (cr=68020 pr=68393 pw=0 time=29346414 us cost=303766 size=669864369 card=223288123)'
STAT #140582923121480 id=6 cnt=2301843 pid=5 pos=1 obj=1464816 op='TABLE ACCESS FULL STOCK_DAY PARTITION: 1 762 (cr=68020 pr=68393 pw=0 time=24376609 us cost=303766 size=669864369 card=223288123)'
when I am trying to measure disk io statistics with iostat it shows that Oracle is issuing a 32K direct path read requests to ASM LUNs. Why? Why not 1M?
Thank you in advance!
Regards,
Kirill
Edited by: Kirill.Boyko on Jan 31, 2013 12:53 PM