ibdata : InnoDB's System Tablespace

ibdata is the usual prefix name of InnoDB's System Tablespace.

The default system tablespace name is ibdata1.

Please note InnoDB Architecture

InnoDB Architecture

From the above diagram, ibdata1 can contain the following:

  1. Data Dictionary
  2. Double Write Buffer (used in Crash Recovery)
  3. Insert Buffer (Used to update Secondary Index change from Buffer Pool)
  4. Rollback Segments
  5. Undo Space
  6. Data Pages from InnoDB Tables (innodb_file_per_table disabled)
  7. Index Pages from InnoDB Tables (innodb_file_per_table disabled)

Adding additional ibdata files results in spreading these seven(7) classes of InnoDB info