NDB Cluster Configuration Files memory. This buffer is used during the local checkpoint phase of a fragment for inserts, deletes, and updates. Because UNDO log entries tend to grow larger as more operations are logged, this buffer is also larger than its index memory counterpart, with a default value of 16MB. This amount of memory may be unnecessarily large for some applications. In such cases, it is possible to decrease this size to a minimum of 1MB. It is rarely necessary to increase the size of this buffer. If there is such a need, it is a good idea to check whether the disks can actually handle the load caused by database update activity. A lack of sufficient disk space cannot be overcome by increasing the size of this buffer. If this buffer is too small and gets congested, the NDB storage engine issues internal error code 891 ( Data UNDO buffers overloaded ). It is not safe to decrease the value of this parameter during a rolling restart. All update activities also need to be logged. The REDO log makes it possible to replay these updates whenever the system is restarted. The NDB recovery algorithm uses a “fuzzy”  checkpoint of the data together with the UNDO log, and then applies the REDO log to play back all changes up to the restoration point. RedoBuffer  sets the size of the buffer in which the REDO log is written. The default value is 32MB; the minimum value is 1MB. If this buffer is too small, the  NDB  storage engine issues error code 1221 ( REDO log buffers overloaded ). For this reason, you should exercise care if you attempt to decrease the value of RedoBuffer  as part of an online change in the cluster’s configuration. ndbmtd  allocates a separate buffer for each LDM thread (see  ThreadConfig ). For example, with 4 LDM threads, an  ndbmtd  data node actually has 4 buffers and allocates  RedoBuffer  bytes to each one, for a total of  4 * RedoBuffer  bytes. 4115 Version (or later) NDB 8.0.13 Type or units bytes Default 8192 Range 0 - 64K Version (or later) NDB 8.0.13 Type or units bytes Default 32M Range 1M - 4294967039 (0xFFFFFEFF) Restart Type N (NDB 8.0.13) Important • RedoBuffer • EventLogBufferSize