InnoDB is a type of InnoDB storage engine in MySQL that supports undo logs and read views.

An undo log is a file in the binary format that stores undo data for transactions that have been executed in an InnoDB database. When a transaction fails, the transaction log is rolled back, and the undo data is stored in the undo log. When a transaction is committed, the transaction log is committed, and the undo data is removed from the undo log. This allows the database to recover from failures by undoing the changes made during a transaction.

Read views are a way to retrieve data from a specific table or view in an InnoDB database. A read view is a virtual table that is created by defining a view query that is stored in the database. When a query is executed against the read view, MySQL returns the data as if it were from the original table.

Both the undo log and read views can be useful for managing transactions and retrieving data in an InnoDB database. The undo log is used to roll back transactions and recover from failures, while the read view is used to retrieve specific data from a table or view.