Suddenly got an “error establishing database connection”

My website which has been online for years, suddenly came up with an “error establishing database connection”.

I added this line to my wp-config.php file:
define(‘WP_ALLOW_REPAIR’, true);
and proceeded to do a database repair. I got a message that several tables were not okay and could not be repaired. What does this mean? The site did come back after I ran this database repair, but is my database corrupted? What should I do at this point?

wp_users: 3 clients are using or haven’t closed the table properly
wp_usermeta: 19 clients are using or haven’t closed the table properly
wp_posts: 20 clients are using or haven’t closed the table properly
wp_comments: 19 clients are using or haven’t closed the table properly
wp_links: 1 client is using or hasn’t closed the table properly
wp_options: Table is marked as crashed
wp_postmeta: 20 clients are using or haven’t closed the table properly
wp_terms: 1 client is using or hasn’t closed the table properly
wp_term_taxonomy: 14 clients are using or haven’t closed the table properly
wp_term_relationships: 13 clients are using or haven’t closed the table properly
wp_commentmeta: 19 clients are using or haven’t closed the table properly