System is running out of memory or swapping
Not enough HugePages to cover the SGA(s) and therefore the area reserved for HugePages are wasted where SGAs are allocated through regular pages.
Review your HugePages configuration to make sure that all SGA(s) are covered.
Databases fail to start
memlock limits are not set properly
Make sure the settings in limits.conf apply to database owner account.
One of the database fail to start while another is up
The SGA of the specific database could not find available HugePages and remaining RAM is not enough.
Make sure that the RAM and HugePages are enough to cover all your database SGAs
Cluster Ready Services (CRS) fail to start
HugePages configured too large (maybe larger than installed RAM)
Make sure the total SGA is less than the installed RAM and re-calculate HugePages.
HugePages_Total = HugePages_Free
HugePages are not used at all. No database instances are up or using AMM.
Disable AMM and make sure that the database instances are up.
Database started successfully and the performance is slow
The SGA of the specific database could not find available HugePages and therefore the SGA is handled by regular pages, which leads to slow performance
Make sure that the HugePages are many enough to cover all your database SGAs
