With 10g many new background processes were introduced.
MMAN Memory Manager (MMAN) coordinates the sizing of different memory components within SGA.
MMAN keeps a track of sizes of components and allocates/de-allocates memory based on their usage.
This process is used only when you enable Automatic Shared Memory Management.
RVWR Process responsible for writing flashback logs which stores pre-image of data-blocks. These logs can be used to flash back database to past point in time. It proves very handy specially in situation of logical data corruptions like an accidental drop/truncate of a table or commit of an unwanted transaction.
CTWR Change Tracking Writer (CTWR) Process introduced in 10g to track changes to block to assist fast RMAN incremental backups. MMNL The Memory Monitor Light (MMNL) process introduced in 10g is responsible for writing out statistics buffer to disk as needed.
It works with Automatic Workload Repository (AWR) MMON The memory monitor (MMON) process was introduced in 10g is responsible for gathering statistics for Automatic Workload Repository.
This helps Oracle doing automatic problem detection and self tuning.
M000 MMON background slave (m000) processes.
RBAL (Re-balancer) is the ASM related process that performs rebalancing of disk resources controlled by ASM.
ARBx These processes are managed by the RBAL process and are used to do the actual rebalancing of ASM controlled disk resources. The number of ARBx processes invoked is directly influenced by the asm_power_limit parameter.
The ASMB process is used to provide information to and from the Cluster Synchronization Services used by ASM to manage the disk resources. It is also used to update statistics and provide a heartbeat mechanism.