应用无法连接数据库，检查oracle发现已经宕机。
     startup 后报错
     ORA-03113: end-of-file on communication channel
     
二、查找原因

查看alter日志
     tail -500 /oracle/database/oracle/diag/rdbms/udb/udb1/trace/alter_UDB1.log
    
     Unable to create archive log file '+FRA/archivelog/1_48359_931010941.dbf'
ARCH: Error 19504 Creating archive log file to '+FRA/archivelog/1_48359_931010941.dbf'
Errors in file /oracle/database/oracle/diag/rdbms/udb/UDB1/trace/UDB1_ora_22183.trc:
ORA-16038: log 1 sequence# 48359 cannot be archived
ORA-19504: failed to create file ""
ORA-00312: online log 1 thread 1: '+DATA/udb/onlinelog/group_1.257.931010945'
ORA-00312: online log 1 thread 1: '+FRA/udb/onlinelog/group_1.257.931010945'

执行archive log list
SQL> archive log list;
Database log mode       Archive Mode
Automatic archival       Enabled
Archive destination       +FRA/archivelog
Oldest online log sequence     48371
Next log sequence to archive   48372
Current log sequence       48372

初步判断是闪回空间剩余容量不足导致的。

三、解决过程

shutdown immediate
startup mount
增大闪回空间容量ALTER SYSTEM SET db_recovery_file_dest_size=20g scope=both;
shutdown immediate 
startup
仍然报错ORA03113
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切换用户su - grid
执行asmcmd命令
执行lsdg 查看目录空间使用情况，发现+FRA目录已经没有free_MB
在+FRA/archivelog目录下手动删除归档日志文件rm -fr ‘1_45*.dbf’
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切换到oracle用户，在rman下检查归档日志
rman>crosscheck archivelog all；
rman>delete expired archivelog all;    (delete archivelog until time 'sysdate-7' ; )
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执行sqlplus / as sysdba
sql>startup

实例正常启动

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