How to increase the size of tinymce applied textarea

Go to tiny_mce/tiny_mce.js and find for o.deltaHeight||0 and change that line to acccording to the height you want like below

h=Math.max(parseInt(h)+(o.deltaHeight||0),100); Usual line, 100 is the default height, you can change it as you want like

h=Math.max(parseInt(h)+(o.deltaHeight||0),300);