ORA-27102: out of memory

The below shows an "ORA-27102 out of memory" error on startup for an Oracle RAC database however this error can occur in single instances also.

$ srvctl start database -d MYDB
PRCR-1079 : Failed to start resource ora.MYDB.db
CRS-5017: The resource action "ora.MYDB.db start" encountered the following error:
ORA-27102: out of memory
SVR4 Error: 22: Invalid argument
. For details refer to "(:CLSN00107:)" in 
"/app/11.2.0/grid/log/myserver01/agent/crsd/oraagent_oracle/oraagent_oracle.log".

In alert log:

WARNING: The system does not seem to be configured
optimally. Creating a segment of size 0x000000009b000000
failed. Please change the shm parameters so that
a segment can be created for this size. While this is
not a fatal issue, creating one segment may improve
performance

9b000000 hex = 2400M = MEMORY_TARGET and MEMORY_MAX_TARGET settings for this particular instance. Check the shared memory max in the project. Databases are being started by the 'grid' user for RAC however single instances will usually be 'oracle':

> projects -l

user.oracle
...
                 project.max-shm-memory=(priv,4294967295,deny)
user.grid
...
                 project.max-shm-memory=(priv,4294967295,deny)

Shared memory maximum allocated to the project is 4G. If the sum of all SGA/PGAs allocated for instances is more than 4G within the project an instance will encounter the error either on startup or even during operation. To fix either increase the maximum shared memory limit (OS resources permitting) or decrease the SGA/PGA in individual instances to under the limit. The following metalink note describes the problem and solutions: Database Startup On Solaris 10 Fails With Ora-27102 Out Of Memory Error [ID 399895.1]