Code of Civil Procedure section 583.310 provides: "An action shall be brought to trial within five years after the action is commenced against the defendant." "Dismissal is mandatory if the action is not brought to trial within the statutory period." (Sanchez v. City of Los Angeles (2003) 109 Cal.App.4th 1262 at p. 1269.) Code of Civil Procedure section 583.630 states: "(a) An action shall be dismissed by the court on its own motion or on motion of the defendant, after notice to the parties, if the action is not brought to trial within the time prescribed in this article. (b) The requirements of this article are mandatory and are not subject to extension, excuse, or exception except as expressly provided by statute." The five-year statutory period may be extended by written stipulation or by oral agreement in open court. (Code Civ. Proc., 583.330.) In addition, with respect to the calculation of the five-year period, Code of Civil Procedure section 583.340 provides: "In computing the time within which an action must be brought to trial pursuant to this article, there shall be excluded the time during which any of the following conditions existed: (a) The jurisdiction of the court to try the action was suspended. (b) Prosecution or trial of the action was stayed or enjoined. (c) Bringing the action to trial, for any other reason, was impossible, impracticable, or futile." In determining whether the tolling provision for impossibility, impracticality or futility specified in Code of Civil Procedure section 583.340 applies, a trial court reviews "all the circumstances of a particular case, including the conduct of the parties and the nature of the proceedings. The critical factor is whether the plaintiff exercised reasonable diligence in prosecuting its case. The statute must be liberally construed, consistent with the policy favoring trial on the merits." (Brown & Bryant v. Hartford Accident & Indem. Co. (1994) 24 Cal.App.4th 247, 251.) Ordinarily, a plaintiff's illness does not render it impossible or impracticable for the plaintiff to bring the matter to trial within the five-year period. (Singelyn v. Superior Court (1976) 62 Cal.App.3d 972, 974.) "The determination 'of whether the prosecution of an action was indeed impossible, impracticable, or futile during any period of time, and hence, the determination of whether the impossibility exception to the five-year statute applies, is a matter within the trial court's discretion. Such determination will not be disturbed on appeal unless an abuse of discretion is shown. ' Where a trial court has discretionary power to decide an issue, we are not authorized to substitute our judgment for that of the trial court. Reversible abuse exists only if there is no reasonable basis for the trial court's action, so that the trial court's decision exceeds the bounds of reason. " (Sanchez v. City of Los Angeles, supra, 109 Cal.App.4th at p. 1271.)