This process is responsible for instance recovery, if necessary, at instance startup. SMON also cleans up temporary segments that are no longer in use. It also coalesces contiguous free extents in dictionary managed tablespaces that have PCTINCREASE set to a non-zero value. SMON wakes up about every 5 minutes to perform housekeeping activities. SMON must always be running for an instance.
This process is responsible for performing recovery if a user process fails. It will rollback uncommitted transactions. PMON is also responsible for cleaning up the database buffer cache and freeing resources that were allocated to a process. PMON also registers information about the instance and dispatcher processes with network listener. PMON wakes up every 3 seconds to perform housekeeping activities. PMON must always be running for an instance.
---****oracle11g新进程****--- VKTM - The virtual keeper of time provides wall-clock time and reference time for other sessions/processes.
FBAR - (sadly now renamed to FBDA partway through the beta) The flashback data archiver writes old row-versions of tables with 'flashback archive' enabled into flashback data archives on commit. Anyone remember Oracle v.5 BIFs?
DIAG - The diagnosibility process (DIAG) runs oradebug commands and triggers diagnostic dumps as part of the new ADR (automatic diagnostic repository) feature, which is a replacement (and major enhancement) for the much-reviled RDA.
DIA0 - The "other" diagnosibility process detects hangs then triggers DIAG do take diagnostics.
SMCO/Wnnn - The space management coordinator and slaves perform space allocation and reclamation.