报错现象：[oracle@node1 ~]$ sqlplus / as sysdba
SQL*Plus: Release 11.2.0.4.0 Production on Thu May 4 15:26:01 2023
Copyright (c) 1982, 2013, Oracle. All rights reserved.
但是三种可能都会有不同差异的报错：
磁盘空间不足或inodes用完：Linux-x86_64 Error： 28： No space left on device
权限不足：Linux-x86_64 Error: 30: Read-only file system 或者 Linux Error: 13: Permission denied
根据上面报错情况，是由于权限不足，经过检查，是因为/U01路径的权限是root:root，修改为Oracle：oinstall之后正常
当inode占用完是，需要删除对应路径下面的一些文件，如下inode已使用100%。
MOS上的一段描述及解决：
Problem Description -------------------
Problem occurs when: $ORACLE_HOME/rdbms/audit directory is full or $ORACLE_HOME/rdbms/audit directory doesn't exist as a side effect of this problem oracle asks for password after connect internal
Solution Description --------------------
Make space available in $ORACLE_HOME/rdbms/audit by removing files that are not needed or Make sure the directory exists and is readable by oracle or Change init.ora audit_file_dest to an existing directory. Change init.ora parameter means restart instance as workaround kill pmon.
Explanation -----------
The behavior on Unix is to write a file named ora_<process_id>.aud into the directory specified by audit_file_dest. The default directory is /rdbms/audit. The file will contain an entry for the audited action, which would be internal logins or startup. On ports which support an OS audit trail, these records will be written there. This feature is not affected by the settings of the audit_trail parameter.
ORA-09925: "Unable to create audit trail file"
Cause: ORACLE was not able to create the file being used to hold audit trail records.
Action: Check the UNIX error number for a possible operating system error.
If there is no error, contact ORACLE customer support.
References ----------
[NOTE:1018924.102] ORA-09925 ON DATABASE STARTUP [NOTE:1056988.6] ORA-09925 DURING HOT BACKUPS [NOTE:21073.1]
OERR: ORA-9925 "Unable to create audit trail [BUG:723955] SQLPLUS ALLOWS DB STARTUP (BUT NOT SHUTDOWN)
IF AUDIT_FILE_DEST DOESN'T EXIST
Search Words ------------ ORA-09925 audit trail audit_file_dest