How To Find Object Name For “wait_resource”

When querying sys.dm_exec_requests dmv, you can see the waiting requests and the resource those requests are waiting for. Sample of such values are shown in Figure 1 below.

Figure 1 – List of wait resources

How do you interpret these values? It has the following format in this case: (It is not always the same format. Depending on the values you see in wait_resource the interpretation would be different)

[database id] : [file id] : [page id]

However still the information is not sufficient because knowing the page id does not give much details related to the issue your troubleshooting. So we need to figure it out the table related to the above page. For that you need to use some undocumented DBCC commands. (Please be careful when running them in production system)

DBCC TRACEON (3604)
GO
DBCC PAGE (5, 20, 56792898)
GO
DBCC TRACEOFF (3604)

You get an output similar to below;

Figure 2 – Output of DBCC PAGE command

Refer the objectId value. That is the object Id of the page belongs to. After that it is simple to find the object name using OBEJCT_NAME() T-SQL function.

Cheers.

Reading a deadlock

Deadlock is a common phenomena in databases where users can work concurrently. Deadlock happens because of pessimistic concurrency control mechanism which is essentially use of locks. You can't prevent deadlocks but of course you need to minimize them occurring. There are several ways of capturing deadlocks in SQL Server. They are;

1. Using SQL Server Profiler

2. Using SQL Server Error Log

The objective of the blog post is to read and understand the deadlock graph which is captured in SQL Server Error log.

Undocumented DBCC Commands

I found this article while searching about DBCC commands. This is really interesting one specially for the people who wants to know SQL Server internals. This article applies for SQL Server 7 and 2000 but I have used some DBCC commands in SQL Server 2005 too. (E.g: DBCC IND, DBCC PAGE)


Since these are undocumented onces you have to use at your risk and no support available from Microsoft.


Useful Undocumented DBCC Commands