There are several important architectural components to an Oracle database system, many of which are added as the new features of Oracle 11g. There are several processes that run the Oracle database code, where some of them are active, while others are run in the background. One of the background processes in Oracle is Space Management Coordinator (SMCO) process (Oracle, 2011c). The main tasks of such process as its title implies is coordinating task which are related to space management, examples of which are proactive space allocation and space reclamation (Oracle, 2011c). SMCO performs theses tasks through spawning slave processes.
Slave processes are those processes which perform tasks on the behalf of other processes, i.e. they initiated by other processes, in this case by SMCO.
An example of the order of processes and tasks that will typically involve space management coordination can be seen through processes related to proactive space management. For example when more than one user implements space related task and commands, the background process SMCO is initiated to dynamically allocate and/ or reclaim space through coordinating the space management tasks (Oracle, 2011b).
The background process does not perform the tasks by itself where it spawns slave processes that has the form Wnnn, where n is a number. Thus, the first slave process spawned by SMCO has the form W000 (Oracle, 2011a). W000 executes the instructions received from SMCO, and if necessary, required slave processes will be spawned additionally with the name W001, W002, etc (Oracle, 2011a).
The principle of operation of W000 process can be seen as follows. Once the slave process is spawned, it will perform tasks such as pre-allocation of space reclaiming space form dropped files, securing file segments. A single database instance, i.e. a memory structure and a background process, can spawn up to 10 Wnnn slave processes. Once spawned such process acts autonomously, performing tasks in the order they are queued.
After a particular idle time, a slave process will be terminated. The interaction between the background processes in SMCO and the slave process it spawns W000, can be seen as an autonomous maintenance tasks, which aim is keeping sure the database is running. As process that belong to the manageability infrastructure such as allocating and reclaiming space is mostly non intrusive and also a background process, SMCO is a common process that can be seen most single instances (Kyte, 2005, p. 190).
References
Kyte, T. (2005). Expert Oracle database architecture : 9i and 10g programming techniques and solutions. Berkeley, Calif.: Apress.
Oracle. (2011a). Oracle Database Concepts: Background Processes. Oracle. Web.
Oracle. (2011b). Oracle Database Concepts: Manageability. Oracle. Web.
Oracle. (2011c). Oracle Database Concepts: Process Architecture. Oracle. Web.