TRAINING (ORA-3) - Database Physical Architecture

Database Physical Architecture



Control Files

> The control file is small, but vital.
> Every database has minimum one control file.
> It contains pointers to the rest of the database: the locations of the online redo log files and of the data files.
> It also stores information required to maintain database integrity: various critical sequence numbers and time stamps.
> The control file will usually be no more than a few megabytes big, but you can’t survive without it.
> Control file maintenance is automatic; your only control is how many copies to have, and where to put them.
> Control file are multiplexed to protect against loss.




Redo Log Files

> Record changes to the database.
> Every database has at least two online redo log files.
> The online redo logs store a continuous chain in chronological order of every change applied to the database. This will be the bare minimum of information required to reconstruct, or redo, changes.
> The redo log consists of groups of redo log files, each file being known as a member.
> Oracle requires at least two groups of at least one member each to function.
> Redo Log files are multiplex to protect against loss.




Data Files
> Oracle stores data physically in data files and logically in tablespaces.
> Data files can belong to only one tablespace and one database.
> Data files are a repository for schema object data.
> Every Database must have two data files, to be created at database creation time.
> With previous releases of Oracle, you could create a database with only one datafile—10g requires two.
> One or more data files could create a single tablespace.