The flashback data archiver process is the key component of the flashback data archive capability—the ability to query data “as of” long periods of time ago (e.g., to query data in a table as it appeared one year ago, five years ago, and so on).
This long-term historical query capability is achieved by maintaining a history of the row changes made to every row in a table over time.
This history, in turn, is maintained by the FBDA process in the background. This process functions by working soon after a transaction commits.
The FBDA process will read the UNDO generated by that transaction and roll back the changes made by the transaction. It will then record these rolled back (the original values) rows in the flashback data archive for us.
DBRM: Database Resource Manager Process
This process implements the resource plans that may be configured for a database instance. It sets the resource plans in place and performs various operations related to enforcing/implementing those resource plans.
The Resource Manager allows the administrators of a database to have fine-grained control over the resources used by the database instance, by applications accessing the database, or by individual users accessing the database.
GEN0: General Task Execution Process
This process provides, as expected by its name, a general task execution thread for the database.
The main goal of this process is to offload potentially blocking processing (processing that would cause a process to stop while it occurs) from some other process and perform it in the background.
For example, if the main ASM process needs to perform some blocking file operation, but that operation could safely be done in the background (ASM can safely continue processing before the operation completes), then the ASM process may request the GEN0 process to perform this operation and let GEN0 notify it upon completion. It is similar in nature to the slave processes described further later in this chapter.