When you EXECUTE a rule from within a current transaction, it suspends the current transaction—known as the parent transaction—and starts a child transaction. The transactions are now nested.
The first transaction started in a user session starts at transaction level one. The session parameter TRANMAXNUM determines the maximum number of transactions that can be nested for a user session.
You can use the $RULENAME shareable tool to find out the name of a rule in the current transaction or in a parent transaction.