The Tiled textures cache controls the size of the cache for tiled EXR and tiled TIFF textures.

UI Path: ||Render Setup window|| > Settings tab > Tiled textures options rollout (Renderer set to V-Ray)

Cache size (MB) – Specifies the size, in megabytes, of the texture cache for tiled OpenEXR and tiled TIFF files. Setting this value to 0 means that V-Ray uses all the available RAM.

Clear cache on render end – Causes V-Ray to clear the texture cache after a render is complete.