We have a client that have written a large number of ad-hoc reports
that they run against the a production server, which then is migrated
to a "backup server) During this migration, the client wants to make
sure that the reports are written in a way that minimises the load
they place on the system - in particular their impact on Sybase's/the
server's ability to satisfy other requests at the same time.
We have told the client that one of the simplest changes that we have
found is to switch to explicitly use Dirty Reads (at Isolation level
0) in almost all cases. This is completely safe as all these adhoc
reports (queries) are running during times that no updates are being
made to the database. Now the cliet has asked two questions:
If there are no updates running, is a Dirty Read any less impactful
than a Read with the default Isolation level?
Is there a way to specify the default Isolation level that is to be
applied at a more global level than on each individual query, while
still controlling the scope of impact - for example by setting an
environment variable for ISQL in each process?
Can someone please help me with this