A writ of mandamus will be denied if a similar application between the same parties on the same matter is already pending before another court.[i] In State ex rel. Horvath v. Rider, 153 Ohio St. 417 (Ohio 1950), the court held that if a prior action is pending between the same litigants involving the same subject matter in a court having jurisdiction, a mandamus proceeding in another court is barred unless it is plain that adequate relief is not obtainable in the prior case. Moreover, the trial court can be compelled to decide a pending matter, if the trial court has erroneously concluded that it lacks jurisdiction to proceed.[ii] The court may deny abatement of a mandamus proceeding because of the pendency of a suit for an injunction if the injunction will merely grant inconclusive relief. If the plaintiff is successful in obtaining the injunction it will still be necessary to enforce payment by a second action in mandamus.
[i] Perry v. Jordan, 34 Cal. 2d 87 (Cal. 1949)
[ii] Green Tree Acceptance, Inc. v. Midwest Federal Sav. & Loan Asso., 433 N.W.2d 140 (Minn. Ct. App. 1988)