Monday 11 July 2011

Finding Object Dependencies In SQL Server

In a sprawling database application, it can sometime be a nightmare if you need to alter the definition of a table, for fear that you will break an object that references it, that you were unaware of. (Although this will all be detailed in your documentation of course! ;-) )

But recently I found a great DMF, which is documented on MSDN, but I had never come across, that given the name of a table, will list all of the Procedures, Functions, Views and Triggers that reference it, and you can join it back to other system object, such as sys.sql_modules to pull back other useful information, such as is the object schema_bound (which will potentially stop you altering the table, and throw an error when you run the ALTER script.)

The DMF is called sys. dm_sql_referencing_entities and the example below will list the details of all objects that depend on a table called mySchema.myTable, along with if the object is schema bound, and even the object’s definition (providing it is not encrypted).


SELECT referencing_schema_name, referencing_entity_name, is_schema_bound, [definition]
FROM sys.dm_sql_referencing_entities ('mySchema.myTable', 'OBJECT') r
INNER JOIN sys.sql_modules m
                ON r.referencing_id = m.object_id

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SSIS - Execute Process Task Hangs When Run From Server Agent

I was faced with an interesting problem recently. I had a SSIS Package that was stored in the Package Store on an ETL Server, and run from a Server Agent job on a Clustered SQL Instance.

If the package was run in Debug mode, it worked perfectly. If it was run from Windows Scheduled Tasks on the Cluster, it also ran perfectly, but when run from Server Agent on the Cluster, it failed.
Or to be more accurate, it didn’t fail! In fact it didn’t do anything! It reached an execute process task that was calling a decompression utility, and sat there, not working, not failing, not doing anything!

Well, I tried the usual things, such as:

Adding SSIS Server to Local Intranet Zone
Turning on Allow Unsafe Files
Using "God Account" to run job
Using "God Account" to Run As on the execute process
Making the owner of the .exe the same account as the execution context of the process
Disable attachment manager

I knew the package and executable worked, so I was sure that it was a OS level setting, but what? Well, I struggled with this, with the aid of an infrastructure team and also MS Technical Support, but the answer finally came from the MSDN Forums, who suggested creating an Environment Variable called SEE_MASK_NOZONECHECKS and setting the Value to 1.

This worked perfectly, but it was an interesting situation, and wanted to share the resolution with you all.


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