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--capture existing value (if current session wasn't changed from the default then it will not be returned)
if object_id('tempdb..#useroptions') > 0
	drop table #useroptions
create table #useroptions (setOption varchar(200), value varchar(50))

insert #userOptions
exec ('DBCC USEROPTIONS')
------------------------------------------------------------

--do your stuff
set transaction isolation level SERIALIZABLE


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--now set it back to whatever it was
declare @isolationlevel varchar(50)
select @isolationlevel = value 
from #useroptions 
where setoption = 'isolation level'

if isNull(@isolationlevel, 'read uncommitted') = 'read uncommitted'
	set transaction isolation level read uncommitted
else if @isolationlevel = 'READ COMMITTED'
	set transaction isolation level read committed
else if @isolationlevel = 'REPEATABLE READ'
	set transaction isolation level REPEATABLE READ
else if @isolationlevel = 'SERIALIZABLE'
	set transaction isolation level SERIALIZABLE
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