What if a CONTROL FILE IS LOST/DAMAGED

Changing Database Parameter Files

It so happened once when one of the filesystems of the UNIX box hung. The db_recover_file_dest was pointing to that location and the database went into hung state.

So we decided to comment out the parameter.

REDO LOG FILES

• Stores a chronological order of every change vector applied to the database
• If a datafile is damaged/destroyed, then it is restored from the last backup + the the change vectors till the datafiles lost
• 2 Types of Redo Log Files
• ONLINE REDO LOG FILES
• ARCHIVE LOG FILES
  
• Online Redo Log consists of groups of Online Redo Log Files
• Minimum 2 groups of Online Redo Log Files required
• Minimum 2 groups are required as when one group is being archived, the other group can be actively accepting the change vectors
• More number of groups of Redo Log Files are maintained for better performance
• More number of members per group are maintained for better security