Connection Problem

[kaywin]

I am using import external data to get a connection and execute the query to populate some values to my sheet..

In one sheet for the columns A to U we have different queries to fill up these column.
I have enabled the option "Refresh when file open" in Data properties.
Since the number of queries is more while opening the excel i am getting an error ORA-12520 "TNS coudnt find handler for requested type of server".

If i delete some of the queries then it is working properly.
Can any one hlp me on this.

Thanks
Kaywin