"Kris Selden" wrote:

> We have a SSIS package that intermittently fails on the deployed server
> (works fine on our dev server) with the following error:
>
> "The variable "%1!s!" is already on the read list. A variable may only be
> added once to either the read lock list or the write lock list."
>
> Not only does it fail only some of the time it also fails on different
> variables, always on an expression and always at the begining.
>
> The variables that are giving the intermittent problems are used in more
> than one expression to initialize other variables or properties.
>
> I'm worried it is executing the expressions on more than one thread and
> ending up on different processors, and the locking scheme doesn't use a
> memory boundary when checking if the variable is already on the readonly list
> before adding it.
>
> Here are some examples:
>
> The following is the *first* 4 messages of one failed run:
> Beginning of package execution
> The variable "User::RefreshFrom" is already on the read list. A variable may
> only be added once to either the read lock list or the write lock list.
> The expression for variable "DeleteRevenueFactQuery" failed evaluation.
> There was an error in the expression.
> An error occurred with the following error message: "The expression for
> variable "DeleteRevenueFactQuery" failed evaluation. There was an error in
> the expression.".
>
> The following is the *first* 3 messages of another failed run:
> Beginning of package execution
> The variable "User::SqlServer" is already on the read list. A variable may
> only be added once to either the read lock list or the write lock list.
> The expression "@[User::SqlServer]" on property "ServerName" cannot be
> evaluated. Modify the expression to be valid.
>