Clear memory once Stored proc completes

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VB

SQL

.NET

Hi
I currently have developed a system of which aprrox 1.3million records are being imported.

Once the files are imported the table that the files are updated in are then updated so that the import mathches the id's of the other tables and the necesary tables can be updated

I have managed to get my process to work though i have been having an issue on my memory that once the process completes it doesnt seem to release the physical memory used.

when the process runs it takes up about 40% of physical memory available

I use the following vb.net code to call my stored procs

using con as new sqlconnection(ConnString)
Con.open()
dim cmd as new sqlcommand
cmd = ("execute proc1",con)
cmd.executenonQuery()
con.close()
end using

there are about 5 stored procs that use this code.

Is there a way that i could release the memory once the process completes?