> RDBMS is an acronym standing for "Relational Data Base
 > Management System".

 > What is the plural of RDBMS.

    The plural of system is systems. So it's like sheep - RDBMS. :-)

 > Is there an apostrophe involved?  Why?  I'm not
 > interested in the possessive, only the plural.

    No.

Best Wishes,
Bill.

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