Symptoms
ORA-01115: IO error reading block from file 393 (block# 2959)
ORA-01110: data file 393: '/u01/proddata/data/ard01.dbf'
ORA-27091: skgfqio: unable to queue I/O
ORA-27027: skgfdisp: I/O error
IBM AIX RISC System/6000 Error: 5 I/O error
- The errors are not reported in the alert log file.
- Running dbv against datafiles from the error messages shows no errors.
- All the mandatory OS patches are applied.
- Oracle patch for Bug 5496862 - IO READING PROBLEMS AFTER INSTALLING IBM TECHNOLOGY LEVEL 5 (5300-05) was installed before patching the OS.
Solutions
Increase maxreqs from 8192 to 12288.
Steps:
1. run aioo -a command to double check current setting for aioo device
2. run aioo -o maxreqs=12288 to set maxreqs dynamically
3. chdev -l aioo -a maxreqs=12288 to set the value of maxreqs permanently for next reboot
4. run aioo -a to confirm change
5. restart oracle
Metalink Note:559697.1
2 comments:
> chdev -l aioo -a maxreqs=12288
The correct form is:
chdev -Pl aio0 -a maxreqs=12288
aio0 is the device name and you need the -P flag as the device is busy, so cannot be changed while in use
NB: AIX 6.1 scales async I/O dynamically.
A very useful and practical troubleshooting guide for Oracle DBAs dealing with ORA-01115, ORA-01110, ORA-27091, and ORA-27072 I/O errors on AIX. The explanation clearly connects the database errors with the underlying asynchronous I/O configuration and provides actionable steps for validating and tuning the maxreqs parameter. The additional clarification regarding the correct chdev syntax and persistent configuration makes this an especially valuable reference for resolving similar production issues efficiently.
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