SSRS Error: An item with the same key has already been added

This typically means that you have an column in your dataset query that is specified twice. For instance, SQL will let you return "Order Number" twice in a query, but if you try to use that query in SSRS, it will error with "An item with the same key has already been added".

Remove the second instance of the column or alias the column to a different name to keep the error from coming back.

SQL Error in the Post Snapshot File for Transactional Replication

When using replication, it is sometimes useful to run a set of commands on the subscribing database either before or after the initial snapshot has been applied. By using a pre-snapshot file, a DBA could remove any dependencies in the subscribing database that would keep the table from being dropped in the event of a re-initialization. We use post-snapshot files to create indexes on the subscribing database that do not exist on the publisher. To find out whether or not pre/post snapshot files are being used, right click on the publication and choose properties. From there, select snapshot and look under the “Run additional scripts” section.

 

So when the subscription is initialized, a snapshot is prepared and placed in the default folder. Along with the bulk copy files, any pre or post snapshot files you are using are placed in there too. So the snapshot is applied to the subscriber and, in this case, a post-snapshot script is ran against the subscribing database. While the snapshot and the post-snapshot scripts are being ran, updates to the replicated tables are being queued for replication in the distribution database. These will be replicated to the subscriber once the snapshot has been applied and the post-snapshot script has completed.

But what happens in the event that the post-snapshot script has an error? The distribution agent considers this to be a failure and retries the post-snapshot script over and over again. While this is happening, updates that are queued for distribution are not being applied to the subscriber. How can we fix this?

One option is to open the post-snapshot file at the location under “Run additional scripts”, fix the error, reinitialize the subscription and re-create the snapshot. This might not be the best option depending on the size of your snapshot and the time it takes to generate it.

The second option is to directly open the post-snapshot file that was copied into the folder when the snapshot was created. By editing the post-snapshot file in the folder specified in the “Put files in the default folder” option, we are directly modifying the SQL that the distribution agent is executing and failing on. If time is critical, you may want to remove all SQL from the file and save it. Note: If you do this, you will have to manually apply the SQL to the subscriber. Once the error in the file either is fixed or the file is cleaned out, the distribution agent will open the file and complete successfully. After that, all the queue updates, inserts and deletes can flow from the publisher to the subscriber.

Subsystem 'CmdExec' could not be loaded (reason: The specified module could not be found)

After a recent server crash, we had the opprotunity to rebuild the SQL Server instance from the previous nights backups. After going through the various steps to restore the Master and MSDB databases, as well as change the location of the tempdb, resource and model databases, we thought everything was set.

Over the weekend, the server in question was set to backup user databases to a file share using SQLCMD. Upon starting the job, the SQL Agent returned the following error message: "Unable to start execution of step 1 (reason: The CMDEXEC subsystem failed to load [see the SQLAGENT.OUT file for details]; The job has been suspended).  The step failed."

After looking throught the SQLAGENT.OUT file (which yielded the same error message), we took a look at the MSDB..SYSSUBSYSTEMS table. Looking in the subsystem_dll column, the issue presented itself.

 SELECT subsystem
               ,subsystem_dll
   FROM msdb..syssubsystems

subsystem  subsystem_dll   
CmdExec    D:\Program Files\Microsoft SQL Server\MSSQL.1\MSSQL\binn\SQLCMDSS90.DLL   

During the server rebuild, the SQL Server program files where installed under the C:\Program Files directory whereas on the crashed server installation, all the old binaries were installed under D:\Program Files. Since we restored the MSDB database from an old backup, those values overwrote the values from the new server install.

In order for the binaries to load, MSDB..SYSSUBSYSTEMS table had to be updated.

UPDATE msdb..syssubsystems
   SET subsystem_dll = REPLACE(subsystem_dll,'D;\','C:\')   
 WHERE subsystem = 'CMDEXEC'

Once the subsystem_dll column has been updated to point to the C:\Program File directory, we restarted the SQL Agent service and checked the SQLAGENT.OUT file again. The error message was gone and the job completed successfully after we restarted it.