Changes to the data of an SAP MaxDB database (AFTER images) are written asynchronously in the log area on the hard disk using a buffer known as the log IO queue.
If the Log-Writer cannot copy the log pages in the log IO queue fast enough, the log IO queue can fill up with pages that have not yet been written. This effect is called the log queue overflow.
All users wishing to make changes have to wait in this situation. The situation can therefore be very critical for performance.
In most cases, log queue overflows occur in the case of write I/O for log volumes being too slow. You must therefore keep in mind that the I/O is not made worse by other actions (possibly because the data area or SWAP area are also contained on the log hard disks,).