Logging considerations for MDC and ITC tables

Index maintenance and logging is reduced when dimensions and therefore block indexes are used, as compared to cases where RID indexes are used.

The database manager removes the BID from the block indexes only when the last record in an entire block is deleted. This index operation is also logged at this time. Similarly, the database manager inserts a BID into the block index only when a record is inserted into a new block. That record must be the first record of a logical cell or an insert to a logical cell of blocks that are currently full. This index operation is also logged at this time.

Because blocks can be 2 - 256 pages of records, this block index maintenance and logging is relatively small. Inserts and deletes to the table and to RID indexes are still logged. For roll out deletions, the deleted records are not logged. Instead, the pages that contain the records are made to look empty by reformatting parts of the pages. The changes to the reformatted parts are logged, but the records themselves are not logged.