ORA-00845: MEMORY_TARGET not supported on this system and ORA-00093: _shared_pool_reserved_min_alloc must be between 4000 and 0

Database not coming up due to below errors (ORA-00845: MEMORY_TARGET not supported on this system and ORA-00093: _shared_pool_reserved_min_alloc must be between 4000 and 0)

Scene 1)

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SQL> startup nomount;

ORA-00845: MEMORY_TARGET not supported on this system

SQL> shut abort

ORACLE instance shut down.

SQL> exit

Disconnected

Scene 2)
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SQL> startup nomount;

ORA-01078: failure in processing system parameters

ORA-00093: _shared_pool_reserved_min_alloc must be between 4000 and 0

SQL> shut abort;

ORACLE instance shut down.

SQL> exit

Disconnected

Scene 3)
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SQL> startup nomount

ORA-01078: failure in processing system parameters

ORA-00838: Specified value of MEMORY_TARGET is too small, needs to be at least 3072M

SQL>

SQL> exit

Disconnected

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These are all due to memory Memory related parameter which is not specified as it should be. 

Solution: 

Scene 1) This error always come if /dev/shm FS size is less then memory target parameter.   

To overcome from this situation either increase the /dev/shm to greater than memory target or keep less value of memory target from /dev/shm. 

Other way is to use SGA_MAX_SIZE instead of MEMORY_TARGET. 

Scene 2) This error only came if SGA_MAX_SIZE is set but aggregate value of  individual memory parameter (db_cache_size, shared_pool_size, java_pool_size, stream_pool_size etc..) value is more than SGA_MAX_SIZE

To overcome from this situation either increase the SGA_MAX_SIZE or decrease aggregate value of  individual memory parameter.

Scene 3) in case by mistaken SGA_MAX_SIZE and MEMORY_TARGET both has been define, and SGA_MAX_SIZE is greater than MEMORY_TARGET. 

To overcome from this situation remove or keep size 0  either SGA_MAX_SIZE or MEMORY_TARGET parameter value

[oracle@abcdbhost01 dbs]$ sqlplus '"as sysdba"

SQL*Plus: Release 11.2.0.3.0 Production on Wed Sep 10 20:48:05 2014

Copyright (c) 1982, 2011, Oracle.  All rights reserved.

Connected to an idle instance.

SQL>  startup nomount

ORACLE instance started.

Total System Global Area 3340451840 bytes

Fixed Size                  2232960 bytes

Variable Size             771755392 bytes

Database Buffers         2550136832 bytes

Redo Buffers               16326656 bytes

SQL>