4 Replies Latest reply: Feb 17, 2014 8:55 AM by user13549752 RSS

    PX Deq Credit: send blkd

    user13549752

      DB:10.2.0.3

      OS:HP-UX

       

      I am getting "PX Deq Credit: send blkd" as the second most TOP WAIT EVENTSin AWR.

       

      Top 5 Timed Events

       

      EventWaitsTime(s)Avg Wait(ms)% Total Call TimeWait Class
      CPU time 310,822 55.6
      PX Deq Credit: send blkd405,18985,13221015.2Other
      db file sequential read20,224,02265,459311.7User I/O
      db file scattered read1,774,09126,619154.8User I/O
      Backup: sbtwrite21,232,85210,44181.9Administrative

       

      Also i can see the Av Rd(ms) for some datafile is like 100,200,300. What can be done to bring it down

        • 1. Re: PX Deq Credit: send blkd
          sybrand_b

          Google came up with Re: PX Deq Credit: send blkd At AWR "Top 5 Timed Events"

           

          I would especially see the comment of Jonathan Lewis.

           

          As to the second question, as you don't provide any information about the physical layout of your database, and this particular datafile, the only recommendation would be to reduce the IO by tuning statements.

           

          -------------

          Sybrand Bakker

          Senior Oracle DBA

          • 2. Re: PX Deq Credit: send blkd
            user13549752

            Hi Sybrand,

             

            For IO could you please tell me what information i can provide

            • 3. Re: PX Deq Credit: send blkd
              sybrand_b

              Hi,

               

              Typically one would use iostat on O/S level to see whether or not the disk is saturated. The disk will be saturated when the number of requests exceeds the maximum number of requests specified by disk vendor.

              From Oracle perspective you would use v$filestat (see V$FILESTAT) which has it's counterpart in the DBA_HIST views used by AWR and OEM.

              Also I am curious about the type of device, ideally everything should be striped and mirrrored, whereas RAID-5 has a write performance penalty, due to the presence of a CRC disk.

               

              ---------------

              Sybrand Bakker

              Senior Oracle DBA

              • 4. Re: PX Deq Credit: send blkd
                user13549752

                device    bps    sps   msps

                 

                 

                   disk3    198   10.5    1.0

                   disk4    101    5.6    1.0

                   disk6     62    7.5    1.0

                   disk8      0    0.1    1.0

                  disk61    277    0.4    1.0

                disk126   8568   18.3    1.0

                disk127   1190    4.2    1.0

                disk158    633    4.9    1.0

                disk159     29    0.3    1.0

                disk161   4820   76.5    1.0

                disk170   2820   34.0    1.0

                disk179  11766   48.6    1.0

                disk188   3068   30.3    1.0

                disk197   3613   37.2    1.0

                disk213   3181   37.2    1.0

                disk215   2809   27.0    1.0

                disk224   7588   44.1    1.0

                disk233   4303   48.5    1.0

                disk242   3141   35.2    1.0

                disk251   4441   53.7    1.0

                disk260   4890   56.8    1.0

                disk276   2728   27.7    1.0

                disk278   2542   24.9    1.0

                disk297    369    2.3    1.0

                disk305    448    4.2    1.0

                disk314   1089    6.9    1.0

                disk324    719    6.3    1.0

                disk333    376    3.2    1.0

                disk342    387    2.2    1.0

                disk351    579    5.5    1.0

                disk359   1269    8.9    1.0

                disk368    883    6.6    1.0

                disk378    557    6.5    1.0

                disk387      2    0.1    1.0

                disk413    730    5.2    1.0

                disk422    709    5.1    1.0

                disk432    586    2.8    1.0

                disk452   1804   10.0    1.0

                disk453   1782   18.7    1.0

                disk454   2359   12.5    1.0

                disk455   1475   10.3    1.0

                disk492   1093    4.6    1.0

                disk493   2071    8.4    1.0

                disk494   2190   17.6    1.0

                disk520    779    5.0    1.0

                disk522    569    4.0    1.0

                disk542   1987    6.4    1.0

                disk554   1241   13.2    1.0

                disk562    892    4.6    1.0

                disk568    370    2.9    1.0

                disk575    673    2.4    1.0

                disk577   1727    9.9    1.0

                disk587   4485   23.1    1.0

                disk596    823    5.8    1.0

                disk619    716    4.4    1.0

                disk620    974    9.0    1.0

                disk637   1310   12.0    1.0

                disk638   1092   10.9    1.0

                disk641     29    0.3    1.0

                disk651      0    0.0    1.0

                disk659     88    0.5    1.0