1、数据库启动报错
SQL> startup
ORACLE instance started.

Total System Global Area 2030043136 bytes
Fixed Size 8794504 bytes
Variable Size 587206264 bytes
Database Buffers 1426063360 bytes
Redo Buffers 7979008 bytes
Database mounted.
ORA-03113: end-of-file on communication channel
Process ID: 1872
Session ID: 1 Serial number: 47660

2、查看告警日志
$tail -100 al*.log
ARCH: STARTING ARCH PROCESSES COMPLETE
2018-10-27T10:35:12.755099+08:00
Errors in file /u01/app/oracle/diag/rdbms/cdb1/cdb1/trace/cdb1_arc0_1874.trc:
ORA-19815: WARNING: db_recovery_file_dest_size of 10485760 bytes is 100.00% used, and has 0 remaining bytes available.
2018-10-27T10:35:12.755152+08:00

You have following choices to free up space from recovery area:

1. Consider changing RMAN RETENTION POLICY. If you are using Data Guard,
   then consider changing RMAN ARCHIVELOG DELETION POLICY.
2. Back up files to tertiary device such as tape using RMAN
   BACKUP RECOVERY AREA command.
3. Add disk space and increase db_recovery_file_dest_size parameter to
   reflect the new space.
4. Delete unnecessary files using RMAN DELETE command. If an operating
   system command was used to delete files, then use RMAN CROSSCHECK and
   DELETE EXPIRED commands.

   ---

   2018-10-27T10:35:12.756113+08:00
   Errors in file /u01/app/oracle/diag/rdbms/cdb1/cdb1/trace/cdb1_arc0_1874.trc:
   ORA-19809: limit exceeded for recovery files
   ORA-19804: cannot reclaim 202974720 bytes disk space from 10485760 bytes limit
   ARC0: Error 19809 Creating archive log file to '/u01/app/oracle/fast_recovery_area/cdb1/CDB1/archivelog/2018_10_27/o1_mf_156%u_.arc'
   krsd_check_stuck_arch: stuck archiver: inactive mandatory LAD:1
   krsd_check_stuck_arch: stuck archiver condition declared

2、处理方法
关闭闪回，不要轻易打开闪回区。
$sqlplus / as sysdba

SQL*Plus: Release 12.2.0.1.0 Production on Sat Oct 27 10:44:15 2018

Copyright (c) 1982, 2016, Oracle. All rights reserved.

Connected to an idle instance.

SQL> startup mount;
ORACLE instance started.

Total System Global Area 2030043136 bytes
Fixed Size 8794504 bytes
Variable Size 587206264 bytes
Database Buffers 1426063360 bytes
Redo Buffers 7979008 bytes
Database mounted.
SQL> show parameter recovery

NAME TYPE VALUE

db_recovery_file_dest string /u01/app/oracle/fast_recovery_area/cdb1
db_recovery_file_dest_size big integer 10M
recovery_parallelism integer 0
remote_recovery_file_dest string

SQL> alter system set db_recovery_file_dest='';

System altered.

SQL> alter database open;

Database altered.

SQL> select open_mode from v$database;

OPEN_MODE

READ WRITE

SQL>