Tex. Gov't Code § 815.5111

The plaintiff shall prosecute with reasonable diligence any suit brought under Section 815.511(f). If the plaintiff does not secure proper service of process or does not prosecute the suit within one year after it is filed, the court shall presume that the suit has been abandoned. The court shall dismiss the suit on a motion for dismissal made by or on behalf of the retirement system unless the plaintiff, after receiving appropriate notice, shows good cause for the delay.