-Increasing SQL priority
Please go and set that back to default. It is not recommended that the priority be increased.
-Increasing Remote query timeout value (its now set to 0, hence unlimited)
That's only of use if the query uses remote servers (openquery, openrowset, 4-part naming)
Is there blocking?
What's the wait type when the invoice takes longer than usual?
Can we see table defintion, index definitions and execution plan?
p.s. It is generally recommended that SQL and Exchange NEVER share the same server due to resource contention.
Microsoft Certified Master: SQL Server, MVP, M.Sc (Comp Sci)SQL In The Wild
: Discussions on DB performance with occasional diversions into recoverability
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