content_image/686781.jpg content_image/686782.jpg
• MaxDiskDataLatency 

<img src='content_image/686781.jpg'>

This parameter controls the maximum allowed mean latency for disk access (maximum 8000 milliseconds). When this limit is reached, NDB  begins to abort transactions in order to decrease pressure on the Disk Data I/O subsystem. Use 0  to disable the latency check. 

• DiskDataUsingSameDisk 

<img src='content_image/686782.jpg'>

Set this parameter to false  if your Disk Data tablespaces use one or more separate disks. Doing so allows checkpoints to tablespaces to be executed at a higher rate than normally used for when disks are shared. 

When DiskDataUsingSameDisk  is true , NDB  decreases the rate of Disk Data checkpointing whenever an in-memory checkpoint is in progress to help ensure that disk load remains constant. 

Disk Data and GCP Stop errors. Errors encountered when using Disk Data tables such as Node nodeid  killed this node because GCP stop was detected  (error 2303) are often referred to as “GCP stop errors” . Such errors occur when the redo log is not flushed to disk quickly enough; this is usually due to slow disks and insufficient disk throughput. 

You can help prevent these errors from occurring by using faster disks, and by placing Disk Data files on a separate disk from the data node file system. Reducing the value of TimeBetweenGlobalCheckpoints tends to decrease the amount of data to be written for each global checkpoint, and so may provide some protection against redo log buffer overflows when trying to write a global checkpoint; however, reducing this value also permits less time in which to write the GCP, so this must be done with caution. 

In addition to the considerations given for DiskPageBufferMemory  as explained previously, it is also very important that the DiskIOThreadPool  configuration parameter be set correctly; having DiskIOThreadPool  set too high is very likely to cause GCP stop errors (Bug #37227). 

GCP stops can be caused by save or commit timeouts; the TimeBetweenEpochsTimeout  data node configuration parameter determines the timeout for commits. However, it is possible to disable both types of timeouts by setting this parameter to 0. 

Parameters for configuring send buffer memory allocation.  Send buffer memory is allocated dynamically from a memory pool shared between all transporters, which means that the size of the send 

