处理故障时，发现startup实例失败，报错ORA-00845: MEMORY_TARGET not supported on this system

SYS@orcl1> startup;
ORA-00845: MEMORY_TARGET not supported on this system

查看alert日志，报错如下

Starting ORACLE instance (normal)
WARNING: You are trying to use the MEMORY_TARGET feature. This feature requires the /dev/shm file system to be mounted for at least 47244640256 bytes. /dev/shm is either not mounted or is mounted with available space less than this size. Please fix this so that MEMORY_TARGET can work as expected. Current available is 46169579520 and used is 21271977984 bytes. Ensure that the mount point is /dev/shm for this directory.
memory_target needs larger /dev/shm

root用户下df -h查看，空闲/dev/shm小于需要47G,

[root@db1 ~]#  df -h
Filesystem           Size  Used Avail Use% Mounted on
/dev/mapper/ol-root  100G   17G   84G  17% /
devtmpfs              63G     0   63G   0% /dev
tmpfs                 63G   22G   42G  35% /dev/shm
tmpfs                 63G  1.1G   62G   2% /run
tmpfs                 63G     0   63G   0% /sys/fs/cgroup
/dev/mapper/ol-home  159G   33G  127G  21% /u01

处理办法：

[root@db1 ~]#  mount -o remount,size=72G /dev/shm
[root@db1 ~]#  df -h
Filesystem           Size  Used Avail Use% Mounted on
/dev/mapper/ol-root  100G   17G   84G  17% /
devtmpfs              63G     0   63G   0% /dev
tmpfs                 72G   22G   51G  31% /dev/shm
tmpfs                 63G  1.1G   62G   2% /run
tmpfs                 63G     0   63G   0% /sys/fs/cgroup
/dev/mapper/ol-home  159G   33G  127G  21% /u01

 再次startup，顺利启动

[root@db1 ~]# su - oracle
Last login: Thu Aug 10 10:18:34 CST 2023 on pts/0
orcl1:/home/oracle@db1> sqlplus / as sysdba

SQL*Plus: Release 11.2.0.4.0 Production on Thu Aug 10 10:22:10 2023

Copyright (c) 1982, 2013, Oracle.  All rights reserved.

Connected to an idle instance.

SYS@orcl1> startup;
ORACLE instance started.

Total System Global Area 4.7034E+10 bytes
Fixed Size            2263936 bytes
Variable Size         2.3354E+10 bytes
Database Buffers     2.3622E+10 bytes
Redo Buffers           55246848 bytes
Database mounted.
Database opened.
SYS@orcl1>

后续处理

方案一、修改/etc/fstab文件，修改后/dev/shm行如下

/dev/shm      tmpfs   defaults,size=72G    0 0

方案二、从AMM调整为ASMM--rac环境待验证

alter system reset memory_max_target scope =spfile sid='orcl1';
alter system reset memory_target=0 scope =spfile sid='orcl1';
alter system set sga_max_size=40G scope=spfile sid='orcl1';
alter system set sga_target=40G scope=spfile sid='orcl1';
alter system set pga_aggregate_target=20G scope=spfile sid='orcl1';

mos文档：ORA-00843, ORA-00849 When Trying To Change SGA_TARGET With MEMORY_MAX_TARGET=0 Being Active (文档 ID 1397761.1)