【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
trace lreg的动态注册过程：SQL> oradebug setospid 12652Oracle pid: 28, Unix process pid: 12652, image: oracle@maclean1.oracle.com (LREG)SQL> oradebug event 10257 trace name context forever,level 16;Statement processed.SQL> alter system register;System altered.SQL> oradebug event 10257 trace name context off;Statement processed.SQL> oradebug tracefile_name;/s01/diag/rdbms/mac/MAC_1/trace/MAC_1_lreg_12652.trc*** 2013-07-08 08:24:25.736kmlwait: status: succ=2, wait=0, fail=0*** 2013-07-08 08:24:26.528Last post from location=FILE:/ade/b/1635153616/oracle/rdbms/src/hdir/kml.h LINE:181 ID:kmmreg, process=2fkmlwait: status: succ=2, wait=0, fail=0kmmlrl: register nowkmmlrl: 89 processeskmmlrl: node load 7kmmlrl: instance load 4kmmgdnu: macc goodness=0, delta=1, pdb=3, flags=0x4:unblocked/not overloaded, update=0x6:G/D/-kmmgdnu: MACXDB goodness=0, delta=1, pdb=0, flags=0x5:unblocked/not overloaded, update=0x6:G/D/-kmmgdnu: MAC goodness=1, delta=1, pdb=0, flags=0x4:unblocked/not overloaded, update=0x6:G/D/-kmmlrl: nsgr update returned 0kmmlrl: nsgr register returned 0kmlwait: LREG woken up to process network events after 0 cskmlwait: status: succ=2, wait=0, fail=0