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

    Warning: async I/O

    76425c46-a19e-4509-b28d-b5c0fbb0b433

      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

          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

            Hi ,

             

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

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

              OS is Linux x86_64

              Database version is =>  11.2.0.3.0

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

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

                • 5. Re: Warning: async I/O
                  mkeskin

                  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