最近给数据库做巡检的时候，总会发现WARNING: aiowait timed out 1 times报错，如下alert的内容：
Thread 1 cannot allocate new log, sequence 52198
Private strand flush not complete
Current log# 5 seq# 52197 mem# 0: /oradb/ADC/sysfile/redo05.log
Thread 1 advanced to log sequence 52198 (LGWR switch)
Current log# 6 seq# 52198 mem# 0: /oradb/ADC/sysfile/redo06.log
Thu Apr 14 05:01:29 2016
WARNING: aiowait timed out 1 times
Thu Apr 14 05:02:03 2016
WARNING: aiowait timed out 1 times
Thu Apr 14 05:02:45 2016
WARNING: aiowait timed out 1 times
Thu Apr 14 05:03:16 2016
minact-scn: useg scan erroring out with error e:12751
Thu Apr 14 05:03:35 2016
WARNING: aiowait timed out 1 times
Thu Apr 14 05:05:16 2016
WARNING: aiowait timed out 1 times
Thu Apr 14 05:07:34 2016
WARNING: aiowait timed out 1 times
Thu Apr 14 05:07:34 2016
WARNING: aiowait timed out 1 times
Thu Apr 14 05:07:34 2016
WARNING: aiowait timed out 1 times
Thu Apr 14 05:07:34 2016
WARNING: aiowait timed out 1 times
Thu Apr 14 05:07:34 2016
WARNING: aiowait timed out 1 times
Thu Apr 14 05:07:35 2016
WARNING: aiowait timed out 1 times
Thu Apr 14 05:10:16 2016
Thread 1 cannot allocate new log, sequence 52199
是数据仓库系统，该段时间正在跑批处理程序，我怀疑是Solaris异步IO的问题，正在和厂商沟通，目前还没反馈。
--20160401
更改了disk_asynch_io，由true改为false，不报错了，但ETL特别慢；又改回为true;
--20160414
更改了db_writer_processes，由20改为28，今晚观察效果；