If select commands that specify readpast also include any of the following clauses, the commands fail and display error messages:
The at isolation clause, specifying 0 or read uncommitted
The at isolation clause, specifying 3 or serializable
The holdlock keyword on the same table
If a select query that specifies readpast also specifies at isolation 2 or at isolation repeatable read, shared locks are held on the readpast table or tables until the statement or transaction completes.
readtext commands that include readpast and that specify at isolation read uncommitted automatically run at isolation level 0 after issuing a warning message.
