【12c新特性】12c中新后台进程，主要包括但不局限于：
| OFSD |
Oracle File Server BG |
| RMON |
rolling migration monitor |
| IPC0 |
IPC Service 0 |
| BW36 |
db writer process 36 |
| BW99 |
db writer process 99 |
| TMON |
Transport Monitor |
| RTTD |
Redo Transport Test Driver |
| TPZ1 |
Test Process Z1 |
| TPZ2 |
Test Process Z2 |
| TPZ3 |
Test Process Z3 |
| LREG |
Listener Registration |
| AQPC |
AQ Process Coord |
| FENC |
IOServer fence monitor |
| VUBG |
Volume Driver Umbilical Background |
| SCRB |
ASM Scrubbing Master |
可以看到这里LREG进程开始负责对Listener Registration监听器的注册：
Service registration enables the listener to determine whether a database service and its service handlers are available. A service handler is a dedicated server process or dispatcher that acts as a connection point to a database. During registration, the LREG process provides the listener with the instance name, database service names, and the type and addresses of service handlers. This information enables the listener to start a service handler when a client request arrives.
Figure 16-5 shows two databases, each on a separate host. The database environment is serviced by two listeners, each on a separate host. The LREG process running in each database instance communicates with both listeners to register the database.
截止目前12c的官方文档中的配图还有问题， 图示还是用PMON注册监听。
Reference:
E16655_01/E16655_01/server.121/e17633/dist_pro.htm#CHDIBHAD