SSIS - Blocking - Syncronization / Asyncronization

All the data flow components can be categorized as synchronous and asynchronous.
They can be further differentiate in

• non-blocking (synchronous)
• semi-blocking (asynchronous)
• fully-blocking (asynchronous).  

Synchronous

• The number of rows input to the synchronous components is equal to the number of rows output from synchronous components
• Components use the same buffer
• All destination components are synchronous
• Non-blocking transformations are synchronized

Asynchronous

• The number of rows output from Asynchronous components may be less\ more than the number of records input to the components (filtration inside)
• Stores all the rows into the memory buffer  before it begins the process of modifying input data to the required output   format.
• They block the data flow in the pipeline until all the input rows are read into the memory E.g. – Sort Transformation- where the   component has to process the complete set of rows in a single operation.
• Components use different buffer
• All source components are asynchronous. they create two buffers; one for the success output and one for the error output.
• Semi\ Full blocking transformations are asynchronous in nature

Synchronous reuse buffers and therefore are generally faster than asynchronous components

Non-Blocking transformations

• Audit
• Character Map
• Conditional Split
• Copy Column
• Data Conversion
• Derived Column
• Lookup
• Multicast
• Percent Sampling
• Row Count
• Script Component
• Export Column
• Import Column
• Slowly Changing Dimension
• OLE DB Command

Semi-blocking transformations

• Data Mining Query
• Merge
• Merge Join
• Pivot
• Unpivot
• Term Lookup
• Union All

Blocking transformations

• Aggregate
• Fuzzy Grouping
• Fuzzy Lookup
• Row Sampling
• Sort
• Term Extraction