When you open a SQL Server Integration Services (SSIS) package in SSIS Designer or add components to a package, SSIS by default checks the data sources used by the various components. This process for SSIS package validation ensures that the external metadata is valid. If the metadata is not valid, you'll receive warning or error messages pointing to the problem. At times, you might want to override the default behavior and open the SSIS package without validation. SSIS supports two properties -- DelayValidation and ValidateExternalMetadata that let you control the validation process on individual components.
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