OS_操作系统的CRONTAB 无法定时自动执行

前两日，客户要求我进行数据同步，我写好了脚本，设置了定时执行，让其在晚上后台自动执行，谁知第二天竟然没有执行。不得已又手动开始执行，

该问题已经遇到过多次，为了彻底解决该问题，今日对该现象进行了分析。

1.查看cron执行日志

查询 /var/adm/cron/log 报错如下：


! 0481-095 The cron job is being rescheduled.
 Mon Jan  4 14:35:00 BEIST 2016
! cron: 0481-087 The c queue maximum run limit has been reached.
 Mon Jan  4 14:35:00 BEIST 2016
! 0481-095 The cron job is being rescheduled.
 Mon Jan  4 14:35:00 BEIST 2016
! cron: 0481-087 The c queue maximum run limit has been reached.
 Mon Jan  4 14:35:00 BEIST 2016
! 0481-095 The cron job is being rescheduled.
 Mon Jan  4 14:35:00 BEIST 2016
! cron: 0481-087 The c queue maximum run limit has been reached.
 Mon Jan  4 14:35:00 BEIST 2016
! 0481-095 The cron job is being rescheduled.
 Mon Jan  4 14:35:00 BEIST 2016
! cron: 0481-087 The c queue maximum run limit has been reached.
 Mon Jan  4 14:35:00 BEIST 2016
! 0481-095 The cron job is being rescheduled.
 Mon Jan  4 14:35:00 BEIST 2016
! cron: 0481-087 The c queue maximum run limit has been reached.
 Mon Jan  4 14:35:00 BEIST 2016
! 0481-095 The cron job is being rescheduled.
 Mon Jan  4 14:35:00 BEIST 2016
! cron: 0481-087 The c queue maximum run limit has been reached.
 Mon Jan  4 14:35:00 BEIST 2016
! 0481-095 The cron job is being rescheduled.
 Mon Jan  4 14:35:00 BEIST 2016
! cron: 0481-087 The c queue maximum run limit has been reached.
 Mon Jan  4 14:35:00 BEIST 2016
! 0481-095 The cron job is being rescheduled.
 Mon Jan  4 14:35:00 BEIST 2016
! cron: 0481-087 The c queue maximum run limit has been reached.
 Mon Jan  4 14:35:00 BEIST 2016
! 0481-095 The cron job is being rescheduled.
 Mon Jan  4 14:35:00 BEIST 2016
! cron: 0481-087 The c queue maximum run limit has been reached.
 Mon Jan  4 14:35:00 BEIST 2016
! 0481-095 The cron job is being rescheduled.
 Mon Jan  4 14:35:00 BEIST 2016
! cron: 0481-087 The c queue maximum run limit has been reached.
 Mon Jan  4 14:35:00 BEIST 2016
! 0481-095 The cron job is being rescheduled.
 Mon Jan  4 14:35:00 BEIST 2016

问题原因：
crontab 没有定时执行是因为“! cron: 0481-087 The c queue maximum run limit has been reached.”。
修改/var/adm/cron/queuedefs 文件。在里面加上这样一句:"c.200j20n60w"，然后kill PID，其中PID为cron进程号,新的cron设置就会生效。
Maximum number of jobs in the queue by default was 50. The errorc messages 0481-087, 0481-095 usually appears when this max. number
is reached. So you can increase the maximum number of jobs in /var/adm/cron/queuedefs , vi the queuedefs file and change
the b to c and the 50 to 200. by including this entry"c.200j20n60w" in the file. After making the changes to the file, 
killcron and it will respawn again with the new settings.
解决方法：
#
#
# here is an example of a low prority (nice 20), 50 entry batch queue
# b.50j20n60w
  c.600j10n120w
在/var/adm/cron/queuedefs/queuedefs加以C队列为1000就可以了。
ps -ef|grep cron
kill -9 con服务的进程号
cron的服务会自动重启，问题解决。

清理cron log文件(400M).