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Problem description: when patrolling, a node database down is found, and an empty instance is displayed when the system is connected through sqlplus. Try to restart the database through startup, prompt MEMORY_TARGETnot supported on this system, view the alarm log and report MEMORY_TARGET failure. The problem can only be solved by increasing / dev/shm size.

The error message of logging in to the database is as follows:

[oracle@db01 ~] $sqlplus / as sysdba

SQL*Plus: Release 11.2.0.4.0 Productionon Mon Oct 30 09:26:35 2017

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

Connected to an idle instance.

SQL > startup

ORA-00845: MEMORY_TARGET not supported on this system

The backend log reports the following information:

Starting ORACLE instance (normal)

WARNING: You are trying to use theMEMORY_TARGET feature. This feature requires the / dev/shm file system to bemounted for at least 13522436096 bytes. / dev/shm is either not mounted or ismounted with available space less than this size. Please fix this so that MEMORY_TARGETcan work as expected. Current available is 12203786240 and used is 454021120bytes. Ensure that the mount point is / dev/shm for this directory.

Memory_target needs larger / dev/shm

Problem analysis:

Because AMM is used in Oracle11g, the system is not supported when MEMORY_TARGET is greater than / dev/shm, thus reporting an error that the database cannot be started. Because / dev/shm is through the size of tmpfs, the problem can be solved by modifying this size in Linux environment.

Solution:

1. View the current tmpfs size information

[oracle@i60001~] $df-h

Filesystem Size Used Avail Use% Mounted on

/ dev/mapper/vg_db01-LogVol02 229G 65G 153G 30% /

Tmpfs 12G 434M 12G 4% / dev/shm-- to be modified here

/ dev/sde1 485m 40m 420m 9% / boot

/ dev/mapper/vg_db01-LogVol00 30G 5.0G 24g 18% / usr

[oracle@i60001~] $mount-o size=20G-onr_inodes=1000000-o noatime,nodiratime-o remount / dev/shm

Mount: onlyroot can do that

To modify the tmpfs size, you need to switch to the root user by following the operations of the root user

[oracle@i60001~] $su root

Password:

2. Modify the tmpfs size

[root@db01oracle] # mount-o size=20G-o nr_inodes=1000000-o noatime,nodiratime-o remount / dev/shm

[root@db01oracle] # df-h

Filesystem Size Used Avail Use% Mounted on

/ dev/mapper/vg_db01-LogVol02 229G 65G 153G 30% /

Tmpfs 20G 434m 20G 3% / dev/shm-- modified size

/ dev/sde1 485m 40m 420m 9% / boot

/ dev/mapper/vg_db01-LogVol00 30G 5.0G 24g 18% / usr

3. After changing the tmpfs size, log in to the database and restart the instance.

[oracle@db01~] $sqlplus / as sysdba

SQL*Plus:Release 11.2.0.4.0 Production on Mon Oct 30 09:42:02 2017

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

Connected toan idle instance.

SQL > startup

ORACLEinstance started.

Total SystemGlobal Area 1.3462E+10 bytes

Fixed Size 2265984 bytes

Variable Size 7381978240 bytes

DatabaseBuffers 6039797760 bytes

Redo Buffers 38014976 bytes

Databasemounted.

Database opened.- shows successful startup

-- query whether the current database instance is normal

SQL > select open_mode from v$database

OPEN_MODE

-

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