| 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。 
D本文转自maclean_007 51CTO博客，原文链接:http://blog.51cto.com/maclean/p2