The population rules for adding DIMMs to the server are as follows:
The Oracle Exadata X8-2 Database Server supports a fixed base configuration of twelve 32 GB DDR4 DIMMs (384 GB). Do not attempt to any install any other DIMM sizes or DIMM types in the server unless you are upgrading the memory with an Exadata memory expansion kit
Populate only the black DIMM slot (channel slot 0) within each memory channel for processors P0 and P1
If you are upgrading the memory to twelve 64 GB DDR4 DIMMs (768 GB), remove the existing 32 GB DIMMs and repopulate the black DIMM slots with 64 GB DIMMs