在Oracle Database 12c中，大量新的后台进程被引入进来，很多新特性的实现都和新的进程有关。如：
- Oracle 12c实现了多LGWR管理，这就引入了LG00-LG99一系列的后台进程；
- Oracle 12c扩展了多DBWR支持，BW36~BW99，这一列进程都会提高DBWR的写并行；
- Oracle 12c的多进程多线程模式 - MPMT，引入SCMN进程作为线程监听进程；
下表对这些进程做了一定的梳理和说明，供大家参考。
| 进程名 | 全名 | 简要描述 | 详细描述 | 组件范畴 |
| AQPC | AQ Process Coordinator | Per instance AQ global coordinator | AQPC is responsible for performing administrative tasks for AQ Master Class Processes including commands like starting, stopping, and other administrative tasks. This process is automatically started on instance startup. | Database instances Advanced Queueing |
| ARSn | ASM Recovery Slave Process（进程范围 ARS0-ARS9） | Recovers ASM transactional operations | The ASM RBAL background process coordinates and spawns one or more of these slave processes to recover aborted ASM transactional operations. These processes run only in the Oracle ASM instance. | Oracle ASM instances |
| BWnn | Database Writer Process | Writes modified blocks from the database buffer cache to the data files | See the Long Description for the DBWn process in this table for more information about the BWnn process. | Database instances |
| FENC | Fence Monitor Process | Processes fence requests for RDBMS instances which are using Oracle ASM instances | CSS monitors RDBMS instances which are connected to the Oracle ASM instance and constantly doing I/Os. When the RDBMS instance terminates due to a failure, all the outstanding I/O's from the RDBMS instance should be drained and any new I/O's rejected. FENC receives and processes the fence request from CSSD. | Oracle ASM instances |
| GCRn | Global Conflict Resolution Slave Process | Performs synchronous tasks on behalf of LMHB | GCRn processes are transient slaves that are started and stopped as required by LMHB to perform synchronous or resource intensive tasks. | Database instances, Oracle ASM instances, Oracle RAC |
| IPC0 | IPC Service Background Process | Common background server for basic messaging and RDMA primitives based on IPC (Inter-process communication) methods. | IPC0 handles very high rates of incoming connect requests, as well as, completing reconfigurations to support basic messaging and RDMA primitives over several transports such as UDP, RDS, InfiniBand and RC. | Oracle RAC |
| LDDn | Global Enqueue Service Daemon Helper Slave | Helps the LMDn processes with various tasks | LDDn processes are slave processes spawned on demand by LMDn processes. They are spawned to help the dedicated LMDn processes with various tasks when certain workloads start creating performance bottlenecks. These slave processes are transient as they are started on demand and they can be shutdown when no longer needed. There can be up to 36 of these slave processes (LDD0-LDDz). | Database instances, Oracle ASM instances, Oracle RAC |
| LGnn | Log Writer Worker | Writes redo log | On multiprocessor systems, LGWR creates worker processes to improve the performance of writing to the redo log. LGWR workers are not used when there is a SYNC standby destination. Possible processes include LG00-LG99. | Database instances |
| LREG | Listener Registration Process | Registers the instance with the listeners | LREG notifies the listeners about instances, services, handlers, and endpoint. | Database instances, Oracle ASM instances, Oracle RAC |
| OFSD | Oracle File Server Background Process | Serves file system requests submitted to an Oracle instance | This background process listens for new file system requests, both management (like mount, unmount, and export) and I/O requests, and executes them using Oracle threads. | Database instances, Oracle RAC |
| QMnn | AQ Master Class Process | Per instance per AQ Master Class Process | Each of this type of process represents a single class of work item such as AQ notification, queue monitors, and cross process. | Database instances Advanced Queueing |
| RM | RAT Masking Slave Process | Extracts and masks bind values from workloads like SQL tuning sets and DB Replay capture files | This background process is used with Data Masking and Real Application Testing. | Database instances |
| RMON | Rolling Migration Monitor Process | Manages the rolling migration procedure for an Oracle ASM cluster | The RMON process is spawned on demand to run the protocol for transitioning an ASM cluster in and out of rolling migration mode. | Oracle ASM instance, Oracle RAC |
| RPOP | Instant Recovery Repopulation Daemon | Responsible for re-creating and/or repopulating data files from snapshot files and backup files | The RPOP process is responsible for re-creating and repopulating data files from snapshots files. It works with the instant recovery feature to ensure immediate data file access. The local instance has immediate access to the remote snapshot file's data, while repopulation of the recovered primary data files happens concurrently. Any changes in the data are managed between the instance's DBW processes and RPOP to ensure the latest copy of the data is returned to the user. | Database instances |
| SAnn | SGA Allocator （SA00 ~ SAzz） | Allocates SGA | A small fraction of SGA is allocated during instance startup. The SAnn process allocates the rest of SGA in small chunks. The process exits upon completion of SGA allocation. | Database instances |
| SCCn | ASM Disk Scrubbing Slave Check Process | Performs Oracle ASM disk scrubbing check operation | SCCn acts as a slave process for SCRB and performs the checking operations. The possible processes are SCC0-SCC9. | Oracle ASM instances |
| SCRB | ASM Disk Scrubbing Master Process | Coordinates Oracle ASM disk scrubbing operations | SCRB runs in an Oracle ASM instance and coordinates Oracle ASM disk scrubbing operations. | Oracle ASM instances |
| SCRn | ASM Disk Scrubbing Slave Repair Process | Performs Oracle ASM disk scrubbing repair operation | SCRn acts as a slave process for SCRB and performs the repairing operations. The possible processes are SCR0-SCR9. | Oracle ASM instances |
| SCVn | ASM Disk Scrubbing Slave Verify Process | Performs Oracle ASM disk scrubbing verify operation | SCVn acts as a slave process for SCRB and performs the verifying operations. The possible processes are SCV0-SCV9. | Oracle ASM instances |
| TTnn | Redo Transport Slave Process | Ships redo from current online and standby redo logs to remote standby destinations configured for ASYNC transport | TTnn can run as multiple processes, where nn is 00 to ZZ. | Database instances, Data Guard |
| VUBG | Volume drive Umbilicus Background | Relays messages between Oracle ASM instance and Oracle ASM Proxy instance that is used by ADVM (for ACFS) | Oracle ASM instances, Oracle ASM Proxy instances |
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