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5 Replies Latest reply: Sep 30, 2013 3:53 AM by mkeskin RSS

Warning: async I/O

76425c46-a19e-4509-b28d-b5c0fbb0b433 Newbie
Currently Being Moderated

Hi,

I get the below warning mesages in the alert log. Is it normal, or is there something that I need to do?

 

Mon Sep 23 18:24:42 2013

Warning: recovery process P003 cannot use async I/O

Mon Sep 23 18:24:42 2013

Warning: recovery process P002 cannot use async I/O

Mon Sep 23 18:24:42 2013

Mon Sep 23 18:24:42 2013

Warning: recovery process P004 cannot use async I/O

Mon Sep 23 18:24:42 2013

Mon Sep 23 18:24:42 2013

Warning: recovery process P005 cannot use async I/O

Warning: recovery process P000 cannot use async I/O

Warning: recovery process P006 cannot use async I/O

 

 

Thanks!

  • 1. Re: Warning: async I/O
    Anar Godjaev Expert
    Currently Being Moderated

    HI

     

    Parallel Query has two components: a foreground process that acts as query coordinator and a set of parallel slaves (Pnnn) that are background processes. These background processes are spawned or reused during the start of a parallel statement. They receive and carry out units of work sent from the query coordinator.

    The maximum number of Pnnn processes is controlled by the initialization parameter PARALLEL_MAX_SERVERS. Slave processes are numbered from 0 to the PARALLEL_MAX_SERVERS setting. If the query is a GV$ query, then these background processes are numbered backward, starting from PZ99.

  • 2. Re: Warning: async I/O
    mkeskin Explorer
    Currently Being Moderated

    Hi ,

     

    Which operating system do you use ? What is database version ?

  • 3. Re: Warning: async I/O
    76425c46-a19e-4509-b28d-b5c0fbb0b433 Newbie
    Currently Being Moderated

    OS is Linux x86_64

    Database version is =>  11.2.0.3.0

  • 4. Re: Warning: async I/O
    76425c46-a19e-4509-b28d-b5c0fbb0b433 Newbie
    Currently Being Moderated

    So does this mean that, I do not have to do anyting about this warning.

  • 5. Re: Warning: async I/O
    mkeskin Explorer
    Currently Being Moderated

    Hi ,

     

    It could be a bug if version matched in this document ( Bug 8656212 - Alert log with message "Warning: recovery process XXXX cannot use async I/O" (Doc ID 8656212.8) ) . Is this affect slow performance  ? You can also open SR , but i think this messages are ignorable. And check below commands , async I/O enabled in your operating system.

     

    Verifying async I/O

     

    If Oracle relinked with async I/O

    $ ldd $ORACLE_HOME/bin/oracle | grep libaio

            libaio.so.1 => /lib64/libaio.so.1 (0x00000031b9e00000)

    $ nm $ORACLE_HOME/bin/oracle | grep io_getevent

                     w io_getevents@@LIBAIO_0.4

    If not relinked

    $ ldd $ORACLE_HOME/bin/oracle | grep libaio

    $ nm $ORACLE_HOME/bin/oracle | grep io_getevent

               w io_getevents

     

    If Linux does not make async I/O calls output like this

    $ egrep "kioctx|kiocb" /proc/slabinfo

    kioctx                0      0     384   0    1 : tunables   54   27    0 : slabdata     17     17      0

    kiocb                 0      0     256   0    1 : tunables  120   60    0 : slabdata      1      1      0

     

    If it does .. ;

     

    $egrep "kioctx|kiocb" /proc/slabinfo

    kioctx               150    170    384   10    1 : tunables   54   27    0 : slabdata     17     17      0

    kiocb                 15     15    256   15    1 : tunables  120   60    0 : slabdata      1      1      0

     

    Check also ;

    $ slabtop

     

     

    Active / Total Objects (% used)    : 495020 / 540926 (91.5%)

    Active / Total Slabs (% used)      : 35181 / 35182 (100.0%)

    Active / Total Caches (% used)     : 114 / 190 (60.0%)

    Active / Total Size (% used)       : 137192.43K / 142783.39K (96.1%)

    Minimum / Average / Maximum Object : 0.02K / 0.26K / 4096.00K

     

     

      OBJS ACTIVE  USE OBJ SIZE  SLABS OBJ/SLAB CACHE SIZE NAME

    202057 168742  83%    0.10K   5461       37     21844K buffer_head

    64320  59300  92%    0.19K   3216       20     12864K dentry

    50208  50168  99%    1.00K  12552        4     50208K ext4_inode_cache

    38665  38420  99%    0.20K   2035       19      8140K vm_area_struct

    24780  22808  92%    0.06K    420       59      1680K size-64

    24540  24060  98%    0.19K   1227       20      4908K filp

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