An OLE DB conn can be made to active directory using an LDAP satement within a sql OPENROWSET statement.
Execution tree = really a thread. Carefull as multi components over single exe tree can be very slow.
Default buffer size = 10Mb
Transactions - Set a parent container to required and it will start a tran - by default all children should be 'supported' so will join it. MS DTC has to be running on the local machine for it to work.
Variables will be set to NULL (look like they disappear) is they are used in an expression which casts them to a size too small. Make sure the cast function has a width that is large enough.
Variable need to have their 'EvaluateAsExpression' set to true if you want to do that. Doesnt default (annoyingly).
Excel driver: only samples some rows to guess data types. Can result in NULLs where data type of row is in minority therefore unexpected: http://technet.microsoft.com/en-us/library/ms141683.aspx.
Flat file driver gives you more control.
OR - set the driver data types in advanced properties.
Error when setting a property with an expression: "cannot be written to the property. The expression was evaluated, but cannot be set on the property" - totally strange as it works in visual studio but not when from inside asp.net app. Crap fix is to restart IIS. Better fix is to go with variable instead.