content_image/726586.jpg content_image/726585.jpg
change rate. In other words, if changes are being written at 10 MByte per second, the checkpoint needs to be written at roughly 26.7 MByte per second. 

Setting RecoveryWork  = 40 means that only 1.4 times the total LCP size is needed (and thus the restore phase takes 10 to 15 percent less time. In this case, the checkpoint write rate is 3.5 times the rate of change. 

The NDB source distribution includes a test program for simulating LCPs. lcp_simulator.cc  can be found in storage/ndb/src/kernel/blocks/backup/ . To compile and run it on Unix platforms, execute the commands shown here: 

shell> gcc lcp_simulator.cc shell> ./a.out 

This program has no dependencies other than stdio.h , and does not require a connection to an NDB cluster or a MySQL server. By default, it simulates 300 LCPs (three sets of 100 LCPs, each consisting of inserts, updates, and deletes, in turn), reporting the size of the LCP after each one. You can alter the simulation by changing the values of recovery_work , insert_work , and delete_work  in the source and recompiling. For more information, see the source of the program. 

• InsertRecoveryWork 

<img src='content_image/726586.jpg'>

Percentage of RecoveryWork  used for inserted rows. A higher value increases the number of writes during a local checkpoint, and decreases the total size of the LCP. A lower value decreases the number of writes during an LCP, but results in more space being used for the LCP, which means that recovery takes longer. This parameter has an effect only when EnablePartialLcp  is true, that is, only when partial local checkpoints are enabled. 

• EnableRedoControl 

<img src='content_image/726585.jpg'>

Enable adaptive checkpointing speed for controlling redo log usage. Set to false  to disable (the default). Setting EnablePartialLcp  to false  also disables the adaptive calculation. 

When enabled, EnableRedoControl  allows the data nodes greater flexibility with regard to the rate at which they write LCPs to disk. More specifically, enabling this parameter means that higher write rates can be employed, so that LCPs can complete and Redo logs be trimmed more quickly, thereby reducing recovery time and disk space requirements. This functionality allows data nodes to make better use 

