will contain one entry for the record for each value of the tagged column. For a given table, columns fall into one of two categories: those which either occur exactly once in each of the records, with possibly a few NULL values; and those which occur rarely, or which may have multiple occurrences in a single record. Fixed and variable columns belong to the former category, while tagged columns belong to the latter. The internal representation of the two column categories is different, and it is important to understand the trade offs between the column categories. Fixed and variable columns are typically represented in every record, even when the occurrence has a NULL value. These columns can be quickly addressed via an offset table. Tagged column occurrences are preceded by a column identifier and the column is located by binary searching the set of tagged columns. Long values Column types of Long Text and Long Binary are large binary objects. They are stored in separate B+tree from the clustered index keyed by long value id and byte offset. ESE supports append, byte range overwrite, and set size for these columns. Also, ESE has a single instance store feature where multiple records may reference the same large binary object, as though each record had its own copy of the information, i.e. without inter-record locking conflicts. The maximum size of a Long Text or Long Binary column value is 2 GB. Version, auto-increment and escrow columns Version columns are automatically incremented by ESE each time a record containing this column is modified via an Update operation. This column cannot be set by the application, but can only be read. Applications of version columns include being used to determine if an in-memory copy of a given record needs to be refreshed. If the value in a table record is greater than the value in a cached copy then the cached copy is known to be out of date. Version columns must be of type Long. Auto increment columns are automatically set by ESE such that the value contained in the column is unique for every record in the table. These columns, like version columns, cannot be set by the application. Auto increment columns are read only, and are automatically set when a new record is inserted into a table via an Update operation. The value in the column remains constant for the life