In this work the dynamic of formation of permanent holographic grating have been investigated. Also the effect of cell thickness and intensity of writing beams on the grating permanency in Azo Dye Doped Liquid Crystals (ADDLC) is studied. Homogeneously aligned pure 1294-1b liquid crystal and doped with Methyl Red (with 1% wt) are used to achieve this purpose. The results are compared with literatures, and showing the optimized properties for constructing an optical memory with high diffraction efficiency and long duration.