Beginning Microsoft SQL Server 2008 ... - S3 Tech Training

Also:
❑ The Sch-S is compatible with all lock modes except the Sch-M.
❑ The Sch-M is incompatible with all lock modes.
❑ The BU is compatible only with schema stability and other bulk update locks.
Specifying a Specific Lock Type — Optimizer Hints
Sometimes you want to have more control over the way the locking goes, either in your query or perhaps
in your entire transaction. You can do this by making use of what are called optimizer hints.
Optimizer hints are ways of explicitly telling SQL Server to escalate a lock to a specific level. They are
included right after the name of the table (in your SQL Statement) that they are to affect.
Optimizer hints are seriously on the advanced side of things. They are often abused by people who are
experienced SQL Server developers, and they are not to be trifled with.
Think of it this way — Microsoft has invested literally millions of dollars in such things as their query
optimizer and knowing what locks to utilize in what situations. Query hints are meant to adjust for the
little things the optimizer may not know about, but in the vast majority of cases you are not going to
know more than their optimizer team did. Shy away from these until the later stages of your SQL Server
learning process (and I promise, I’ll cover them well in the Professional version of this book).
Determining Locks Using the Management Studio
Chapter 14: Transactions and Locks
Perhaps the nicest way of all to take a look at your locks is using the Management Studio. The Management
Studio will show you locks in two different sorts — by process ID or by object — utilizing the Activity
Monitor.
To make use of the Management Studio’s lock display, just navigate to the ➪ Activity Monitor
node of the Management Studio, where is the top level node for the server you want to monitor
activity on. SQL Server should come up with a new window that looks something like Figure 14-3.
Just expand the node that you’re interested in (the Overview section is expanded by default — I’ve manually
expanded the Processes section) and you can scroll around to find a large number of metrics —
including whatever locks are currently active on the system.
Perhaps the coolest feature of the Activity Monitor is that when you right-click on a specific process in
the Process window, you get the option of easily starting a SQL Profiler trace against that particular
process. This can be very handy when you are troubleshooting a variety of situations.
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