If one of your dbspaces is becoming full, you might want to add a new chunk. Before you do, however, you must first allocate disk space as described in Allocating Disk Space.
You add a chunk when you need to increase the amount of disk space allocated to a storage space. To add a chunk, you must be logged in as user informix or root.
If you are adding a chunk to a mirror storage space, you must also add a mirror chunk.
When you add a chunk that is allocated as a cooked file, the database server verifies that the disk space is sufficient for the new chunk by creating and then removing a file of the size requested. If the size of the chunk is greater than the available space on the disk, the database server might inadvertently fill your file system in the process of verifying available disk space.
To add a chunk to a dbspace, use the onutil utility.