The block can change depending on the user viewing the page. This setting can be resource-consuming for sites with large number of users, and thus should only be used when BLOCK_CACHE_PER_ROLE is not sufficient.
File
- modules/
block/ block.module, line 51 - Controls the boxes that are displayed around the main content.
Code
define('BLOCK_CACHE_PER_USER', 0x0002)