Do selects block truncates?

Hi all:

I am running oracle 10.2.0.2 and I see two sessions running truncate commands being stuck. It looks like they are waiting on another session which is currently running a long select. That select accesses both of the tables that
the other two sessions are trying to truncate. I was not aware that a select can block a truncate. Is that the case or is there something else here which I am missing?

thank you

Gene Gurevich

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