The "land of oblivion" is a way of referring to the place of the dead. Oblivion means a state of being completely forgotten or no longer remembered. It can also mean being unaware of what is happening. The phrase suggests that both God and living people forget those who have died (Psalm 88:12). People forget them too (Ecclesiastes 9:5–6). However, Job 14:21–22 suggests that those who have died can sense some things in Sheol.
See also Sheol.