The SYSTEM tablespace always contains the data dictionary tables. Data dictionary
tables that are preceded by the V$ or GV$ prefixes are dynamic tables, which are
continually updated to reflect the current state of the Oracle database. Static data
dictionary tables can have a prefix such as DBA_, ALL_, or USER_ to indicate the
scope of the objects listed in the view.
Processes or Threads?
With all this talk about processes, you may be wondering whether Oracle actually uses
threads or processes in the underlying operating system to implement these services.
For simplicity, throughout this book we use the term process generically to indicate a
function that Oracle performs, such as DBW or LGWR. For Oracle on Windows, each
???Oracle process??? is a thread within a process. For Oracle on Unix, the ???processes??? are
more commonly actual operating system processes, not threads. Thus, on Unix DBW
and LGWR are specific operating system processes, while on Windows they are
threads within a single process.
There are some exceptions, however, and how the database is implemented at this level
of detail can be both database version and operating system dependent.
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