Playing with the twisted adbapi connecting to oracle. Stressing a bit the application (an sftp server authenticating on oracle) I found that when the connection pool is exhausted the application crashed.
The (simple) solution is to instantiate the pool with the threaded keyword.
dbpool = adbapi.ConnectionPool("cx_Oracle", uri, threaded=True )
Twisted is an event-based framework: all the blocking calls should be done outside the listening thread. The a(synchronous)dbapi provide separate threads for db connections. Using cx_oracle in a non thread-safe way is a reasonable cause of segfault.
So checking cx_Oracle docs we found that thread safety is off by default to gain some performance.