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Download Performance Guide for IBM Informix Dynamic Server
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Case Study 3. To determine the dbspaces that account for the I/O load, use onstat -d, as Figure A-3 shows. Dbspaces address number flags c009ad00 1 1 c009ad44 2 2001 c009ad88 3 1 c009adcc 4 1 c009ae10 5 2001 c009ae54 6 1 c009ae98 7 1 c009aedc 8 1 c009af20 9 1 9 active, 32 total Chunks address chk/dbs offset c0099574 1 1 500000 c009960c 2 2 510000 c00996a4 3 3 520000 c009973c 4 4 530000 c00997d4 5 5 500000 c009986c 6 6 510000 c0099904 7 7 520000 c009999c 8 8 545000 c0099a34 9 9 250000 c0099acc 10 9 250000 c0099b64 11 9 250000 11 active, 32 total fchunk 1 2 3 4 5 6 7 8 9 size 10000 10000 10000 250000 10000 10000 25000 10000 450000 450000 450000 nchunks 1 1 1 1 1 1 1 1 3 free 9100 9947 9472 242492 9947 2792 11992 9536 4947 4997 169997 flags N N T N N N T N N N N bpages owner informix informix informix informix informix informix informix informix informix flags POPOPOPOPOPOPOPOPOPOPO- name rootdbs tmp1dbs oltpdbs histdbs tmp2dbs physdbs logidbs runsdbs acctdbs Figure A-3 Display from the onstat -d option pathname /dev/infx2 /dev/infx2 /dev/infx2 /dev/infx2 /dev/infx4 /dev/infx4 /dev/infx4 /dev/infx4 /dev/infx5 /dev/infx6 /dev/infx7 In the Chunks output, the pathname column indicates the disk device. The chk/dbs column indicates the numbers of the chunk and dbspace that reside on each disk. In this case, only one chunk is defined on each of the overloaded disks. Each chunk is associated with dbspace number 9. The Dbspaces output shows the name of the dbspace that is associated with each dbspace number. In this case, all three of the overloaded disks are part of the acctdbs dbspace. Although the original disk configuration allocated three entire disks to the acctdbs dbspace, the activity within this dbspace suggests that three disks are not enough. Because the load is about equal across the three disks, it does not appear that the tables are necessarily laid out badly or improperly fragmented. However, you could get better performance by adding fragments on other disks to one or more large tables in this dbspace or by moving some tables to other disks with lighter loads. A-4 Performance Guide for IBM Informix Dynamic Server
