场景
数据库启动时报错。关闭前还是正常运行的，再次启动时，就报了以下错误。
Copyright (c) 1982, 2013, Oracle. All rights reserved. Connected to an idle instance. SQL> startup ORACLE instance started. Total System Global Area 784998400 bytes Fixed Size 2257352 bytes Variable Size 515903032 bytes Database Buffers 264241152 bytes Redo Buffers 2596864 bytes ORA-00205: error in identifying control file, check alert log for more info SQL> exit Disconnected from Oracle Database 11g Enterprise Edition Release 11.2.0.4.0 - 64bit Production With the Partitioning, OLAP, Data Mining and Real Application Testing options
分析
上数据库关闭时，数据库运行正常。关闭数据库后，就立即关闭了服务器。这次开启服务器，再开启数据库时，就报了该错误。怀疑是系统的原因更大一些，就试着重启了一下系统，再启动数据库时，就能正常启动了。然后查阅一些资料。
Oracle 官方对于ORA-00205的分析
Versions 10.2, 11.1, 11.2, 12.1
Error: ORA-00205 error in identifying control file, check alert log for more info
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Cause: The system could not find a control file of the specified name and
size.
Action: Check that ALL control files are online and that they are the same
files that the system created at cold start time.
Database Bugs Related to ORA-00205
Errors are usually due to usage, application or configuration issues but in some cases they may be caused by a bug issue. This section lists any database bugs that have been linked to error "ORA-205" .
总结
ORA-00205可能是因为数据库在启动时无法正常读取控制文件，但这并不表示控制文件损坏，可能是系统由于某种原因导致数据库无法读取，也可能是其他原因；可能重启系统再次启动库，或者在系统层面查看控制文件的信息，确认其是否正常。