backup log is terminating abnormally because for write on file failed: 112(error not found)

昨天遇到一个案例，YourSQLDba做事务日志备份时失败，检查YourSQLDba输出的错误信息如下:

<Exec>

<ctx>yMaint.backups</ctx>

<Sql>

backup log [gewem]

to disk = 'M:\DB_BACKUP\LOG_BACKUP\xxxx_[2016-11-22_01h11m05_Tue]_logs.TRN'

with noInit, checksum, name = 'YourSQLDba:16h16: M:\DB_BACKUP\LOG_BACKUP\xxxx_[2016-11-22_01h11m05_Tue]_logs.TRN'

</Sql>

<err>Error 3202, Severity 16, level 2 : Write on "M:\DB_BACKUP\LOG_BACKUP\xxxx_[2016-11-22_01h11m05_Tue]_logs.TRN" failed: 112(error not found)

Error 3013, Severity 16, level 1 : BACKUP LOG is terminating abnormally.

</err>

</Exec>

这个“failed :112”信息一出现，意味着肯定是磁盘空间不够，昨天总结的那篇博客DBCC CHECKDB 遭遇Operating system error 112(failed to retrieve text for this error. Reason: 15105) encountered其实遇到的问题也是类似的，Operating System error 112 meaning There is not enough space on the disk.

当时检查时，发现磁盘空间还剩下十多G，然后自己手工又将代码取出，手工执行测试，依然报这个错误:

backup log [xxxx] 

to disk = 'M:\DB_BACKUP\LOG_BACKUP\xxxx_[2016-11-22_01h11m05_Tue]_logs.TRN' 

with noInit, checksum, 

NAME = 'YourSQLDba:00h10: M:\DB_BACKUP\LOG_BACKUP\xxxx_[2016-11-22_01h11m05_Tue]_logs.TRN'

后面检查发现这个数据库的日志文件暴增，已经超过数据文件的大小。如下截图所示，所以即使磁盘空间还有不少（19G），部署的磁盘空间告警作业亦正常，没有出现告警，但是已经不能足够支撑事务日志备份完成。所以出现了这个问题，问题有点隐蔽，不过只要细心，问题真相就能水落石出。剔除几个老旧备份以及已经上带的备份,腾出了一些磁盘空间,重新运行作业,作业执行成功!