I've tried to run this
'alter database mydb
set read_write'

in my DTS (Execute SQL Task ) but it seem has a trouble the process
can't stop ... but if i run it in query analyzer it can run and finish
immediately

How come this can be happen ?

Have you checked master..sysprocess table to see what the status of this
process is?

I've already checked it , the status is sleeping...

obtaining the ip address of connection
Use a stored procedure from a function
triggers
Anything better than TSQL?
Urgent! - time out errors while inserting into the dB