• ndb_autoincrement_prefetch_sz changes.  In NDB 8.0.19, the default value of the ndb_autoincrement_prefetch_sz  server system variable is increased to 512. 

• Changes in parameter maxmimums and defaults.  NDB 8.0.19 makes the following changes in configuration parameter maximum and default values: 

•The maximum for DataMemory  is increased to 16 terabytes. 

•The maximum for DiskPageBufferMemory  is also increased to 16 terabytes. 

•The default value for StringMemory  is increased to 25%. 

•The default for LcpScanProgressTimeout  is increased to 180 seconds. 

• Disk Data checkpointing improvements.  NDB Cluster 8.0.19 provides a number of new enhancements which help to reduce the latency of checkpoints of Disk Data tables and tablespaces when using non-volatile memory devices such as solid-state drives and the NVMe specification for such devices. These improvements include those in the following list: 

•Avoiding bursts of checkpoint disk writes 

•Speeding up checkpoints for disk data tablespaces when the redo log or the undo log becomes full 

•Balancing checkpoints to disk and in-memory checkpoints against one other, when necessary 

•Protecting disk devices from overload to help ensure low latency under high loads 

As part of this work, NDB 8.0.19 introduces two new data node configuration parameters. MaxDiskDataLatency  places a ceiling on the degree of latency permitted for disk access and causes transactions taking longer than this length of time to be aborted. DiskDataUsingSameDisk  makes it possible to take advantage of housing Disk Data tablespaces on separate disks by increasing the rate at which checkpoints of such tablespaces can be performed. 

In addition, three new tables in the ndbinfo  database, also added in NDB 8.0.19 and listed here, provide information about Disk Data performance: 

•The diskstat  table reports on writes to Disk Data tablespaces during the past second 

•The diskstats_1sec  table reports on writes to Disk Data tablespaces for each of the last 20 seconds 

•The pgman_time_track_stats  table reports on the latency of disk operations relating to Disk Data tablespaces 

• Memory allocation and TransactionMemory.  NDB 8.0.19 introduces a new TransactionMemory parameter which simplifies allocation of data node memory for transactions as part of the work done 

