At the very beginning when Exadata appeared at 2010 the settings of Linux OS and Oracle RDBMS were configured to use flat memory. There were no NUMA settings despite the SUN 4275 server is actualy NUMA server. And some notes at old times prohibited using NUMA settings on the Exadata.
But starting from November 2018 (Exadata image 18.10), Oracle silently enabled NUMA settings for Exadata. Which can increase appearance of ORA-04031.
Here is a some words about enabling NUMA on Exadata in 2378765.1:
" Normally, PX message buffers come out of the large pool as long as sga_target or memory_target is set. However, when "_enable_NUMA_support" is 'TRUE' and you are running on Exadata (then _px_numa_support_enabled is 'TRUE') causes PX message buffers to be allocated from the numa pool. "
But starting from November 2018 (Exadata image 18.10), Oracle silently enabled NUMA settings for Exadata. Which can increase appearance of ORA-04031.
Here is a some words about enabling NUMA on Exadata in 2378765.1:
" Normally, PX message buffers come out of the large pool as long as sga_target or memory_target is set. However, when "_enable_NUMA_support" is 'TRUE' and you are running on Exadata (then _px_numa_support_enabled is 'TRUE') causes PX message buffers to be allocated from the numa pool. "
