REDOLOG FILE:
• Redo log buffer contains committed and uncommitted data
• Server process goto data buffer then datafile.
• Server process only read data.
• When state of data in Buffer cache change, because of update etc, then it is called dirty buffer.
• Pinned: Multiple session write same block and other session wait.
• Clean: unpinned and ready to aged out when not referenced again
• Free or Unused: empty buffer when instance started
• Dirty: No longer pinned and change and flush to disk by DBWn
Control File:
Having info of DB structure.
Have atleast 1 control file
If more than one, all should have mirrored
Data file:
Data of user and application.
Redo Log files:
Have change data
By default 3 files
Min-2 and max 255
Log writer writes in 5 conditions.
When 1 MB full
Every 3 sec
When 1/3 full
At commit
At checkpoint
Work on circular fashion.
• The Redo Log file to which LGWR is actively writing is called the current log file.
• Log files required for instance recovery are categorized as active log files.
• Log files no longer needed for instance recovery are categorized as inactive log files.
• Default is two ARCn processes – you can specify up to 10 processes.
Parameter File:
Contains info of parameters require when instance start. (Shared pool size, buffer cache size etc)
Init.ora, spfile, pfile
Shutdown Immediate:
SYSTEM and SYSAUX:
SYSTEM: core functionality, data dictionary table (Meta data info).
SYSAUX: working and tables of enterprise manager.
Can be make offline. But database not stop.
Storage Hierarchy:
Table Space ( Segment ( multiple extents ( data blocks
One data file belong to one table space
A BLOCK is the smallest allocation unit. 2K to 32K.
Segment: is a set of extents. It is logical storage unit
1- Data Segment 2-Index Segment 3- Undo Segment 4- Temporary Segment
Tablespace:
• Table space is a logical storage...