To find the value of \( a \) such that the point \( (a, 2) \) satisfies the logarithmic equation \( y = \log_3 x \), we can substitute \( y = 2 \) into the equation:
\[ 2 = \log_3 a \]
Now we need to convert the logarithmic equation to its exponential form. The equation \( \log_3 a = 2 \) means that:
\[ a = 3^2 \]
Calculating \( 3^2 \):
\[ a = 9 \]
Therefore, the value of \( a \) is:
\[ \boxed{9} \]