persistent

adjective

• Obstinately refusing to give up or let go.

  "She has had a persistent cough for weeks."

• Insistently repetitive.

  "There was a persistent knocking on the door."

• Indefinitely continuous.

  "There have been persistent rumours for years."

• Lasting past maturity without falling off.

  "Pine cones have persistent scales."

• Of data or a data structure: not transient or temporary, but remaining in existence after the termination of the program that creates it.

  "Once written to a disk file, the data becomes persistent: it will still be there tomorrow when we run the next program."

• Describing a fractal process that has a positive Brown function
• (stochastic processes, of a state) non-transient.