The Foreach Loop container is a powerful tool in SQL Server Integration Services (SSIS) that allows developers to perform operations on a set of files with unknown filenames. Despite its usefulness, it is often underutilized due to a lack of documentation. In this article, we will explore how the Foreach Loop container can be used to solve a common problem in SQL Server log shipping.
Problem: Deleting Log Files
In log shipping, it is common to have limited disk space. As a result, it becomes necessary to delete log files as soon as they are no longer needed. However, this process needs to be automated and failsafe. The Foreach Loop container provides a solution to this problem.
Setting the Stage
Before we dive into the solution, let’s set the stage by defining the necessary connections and variables. In our SSIS package, we will define two connections: one to the SQL log shipping monitor/target server and another to TEMPDB on the target SQL server. Additionally, we will define four package-scoped variables that will be used throughout the process.
Building the List of Files
The first step is to populate a temporary table with a list of files found in a given folder. To achieve this, we will add a Foreach Loop Container to the package. We will configure the container to iterate through each file in the folder and update a variable with the file name. This variable will be used in an Execute SQL task to insert the file name into the temporary table.
Checking Which Files Can Be Safely Deleted
Once we have a table with a complete list of files, we need to determine which files can be safely deleted. In our case, we want to ensure that the backup files have been correctly restored on the log shipping target server before deleting them. To accomplish this, we will create a Data Flow task that queries the temporary table and joins it with the system table used by SQL to store the restore status. The result set will be a list of filenames that can be safely deleted.
Deleting the Files
With the list of files that can be safely deleted, we can now proceed to delete them. We will use another Foreach Loop Container to iterate through the list and delete each file one-by-one. To achieve this, we will use a Script task to convert the file name from an object to a string that can be used in a File System Task. The File System Task will perform the actual deletion of the files.
Conclusion
The Foreach Loop container is a versatile tool in SQL Server Integration Services that allows developers to perform operations on a set of files with unknown filenames. In this article, we have explored how it can be used to automate the deletion of log files in SQL Server log shipping. By leveraging the power and flexibility of the Foreach Loop container, developers can create robust and efficient SSIS packages.
References:
- Foreach Loop Container – Microsoft Docs
- SQL Server Integration Services (SSIS) Foreach Loop Container – SQL Shack
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