[Note from Pinal]: This is a 41th episode of Notes from the Field series. The real world is full of challenges. When we are reading theory or book, we sometimes do not realize how real world reacts works and that is why we have the series notes from the field, which is extremely popular with developers and DBA. Let us talk about interesting problem of how to figure out what has changed in the DELETED database. Well, you think I am just throwing the words but in reality this kind of problems are making our DBA’s life interesting and in this blog post we have amazing story from Brian Kelley about the same subject.
In this episode of the Notes from the Field series database expert Brian Kelley explains a how to find out what has changed in deleted database. Read the experience of Brian in his own words.
Sometimes, one of the hardest questions to answer is, “What changed?” A similar question is, “Did anything change other than what we expected to change?”
The First Place to Check – Schema Changes History Report:
Pinal has recently written on the
Schema Changes History report and its requirement for the Default Trace to be enabled. This is always the first place I look when I am trying to answer these questions.
There are a couple of obvious limitations with the Schema Changes History report. First, while it reports what changed, when it changed, and who changed it, other than the base DDL operation (CREATE, ALTER, DELETE), it does not present what the changes actually were. This is not something covered by the default trace. Second, the default trace has a fixed size. When it hits that
size, the changes begin to overwrite. As a result, if you wait too long, especially on a busy database server, you may find your changes rolled off.
But the Database Has Been Deleted!
Pinal cited another issue, and that’s the inability to run the Schema Changes History report if the database has been dropped. Thankfully, all is not lost.
One thing to remember is that the Schema Changes History report is ultimately driven by the Default Trace. As you may have guess, it’s a trace, like any other database trace. And the Default Trace does write to disk. The trace files are written to the defined LOG directory for that SQL Server instance and have a prefix of log_:
Therefore, you can read the trace files like any other.
Tip: Copy the files to a working directory. Otherwise, you may occasionally receive a file in use error.
With the Default Trace files, if you ask the question early enough, you can see the information for a deleted database just the same as any other database.
Testing with a Deleted Database:
Here’s a short script that will create a database, create a schema, create an object, and then drop the database. Without the database, you can’t do a standard Schema Changes History report.
CREATE DATABASE DeleteMe;
CREATE SCHEMA Test AUTHORIZATION dbo;
CREATE TABLE Test.Foo (FooID INT);
DROP DATABASE DeleteMe;
This sets up the perfect situation where we can’t retrieve the information using the Schema Changes History report but where it’s still available.
Finding the Information:
I’ve sorted the columns so I can see the Event Subclass, the Start Time, the Database Name, the Object Name, and the Object Type at the front, but otherwise, I’m just looking at the trace files using SQL Profiler. As you can see, the information is definitely there:
Therefore, even in the case of a dropped/deleted database, you can still determine who did what and when. You can even determine who dropped the database (loginame is captured). The key is to get the default trace files in a timely manner in order to extract the information.
If you want to get started with performance tuning and database security with the help of experts, read more over at Fix Your SQL Server.
Reference: Pinal Dave (http://blog.sqlauthority.com)