Response
You need to free space on or add space to the device in which the forest is stored. If your forest is also in the error state (XDMP-FORESTERR), then you can perform the following to get it out of the error state:
Disable automatic merges on the forest.
Restart the forest.
Delete some documents from the forest.
Start a manual merge on the forest.
Stack Overflow: Get the most useful answers to questions from the MarkLogic community, or ask your own question.