ERROR
ORA-04030: out of process memory when trying to allocate 4088 bytes while ADOP in 12.2.3
SOLUTION
Restart of the adworker fixed the issue.
OR
Change the page count to 200000 at the OS level:
$ more /proc/sys/vm/max_map_count
$ sysctl -w vm.max_map_count=200000
OR
Adjust the realfree heap pagesize within the database by setting the following parameters in the init/spfile and restart the database.
_use_realfree_heap=TRUE
_realfree_heap_pagesize_hint = 262144
Then try restarting the worker