Improved performance for read operations.

git-svn-id: http://h2database.googlecode.com/svn/trunk@5332 e6896862-9d19-0410-bfb3-e9fa5d50e656
Documentation.

git-svn-id: http://h2database.googlecode.com/svn/trunk@5333 e6896862-9d19-0410-bfb3-e9fa5d50e656