It will be necessary before any arbitration to conduct discovery. This means that there needs to be an inquiry to determine the scope and extent of all assets.
In California, under the Family Code, each party is required to disclose, under penalty of perjury, in the Preliminary Declaration of Disclosure, any and all assets. If assets are hidden and not disclosed, the court retains the power indefinitely to divide the assets when discovered and disclosed.
You should not go to any arbitration or mediation until you have a whole and complete understanding of all assets. This means that inquiry and discovery of those assets must be done before the mediation or arbitration process begins.