Oracle 5.0 Reference Manual page 1612

Effective Version
MySQL 5.0.0
Restart Type: N
This parameter is a boolean value, and is disabled by default. When
checksums are calculated for all messages before they are placed in the send buffer. This feature
prevents messages from being corrupted while waiting in the send buffer. It also serves as a check
against data being corrupted during transport.
17.3.2.11. Configuring MySQL Cluster Parameters for Local Checkpoints
The parameters discussed in
String Memory [1558]
isolation, but rather are very much interdepedent on each other. In this section, we illustrate how these
parameters—including DataMemory, IndexMemory, NoOfDiskPagesToDiskAfterRestartTUP,
NoOfDiskPagesToDiskAfterRestartACC, and NoOfFragmentLogFiles—relate to one another
in a working Cluster.
In this example, we assume that our application performs the following numbers of types of operations
per hour:
• 50000 selects
• 15000 inserts
• 15000 updates
• 15000 deletes
We also make the following assumptions about the data used in the application:
• We are working with a single table having 40 columns.
• Each column can hold up to 32 bytes of data.
• A typical
UPDATE
• No
NULL
A good starting point is to determine the amount of time that should elapse between local checkpoints
(LCPs). It is worth noting that, in the event of a system restart, it takes 40-60 percent of this interval
to execute the REDO log—for example, if the time between LCPs is 5 minutes (300 seconds), then it
should take 2 to 3 minutes (120 to 180 seconds) for the REDO log to be read.
The maximum amount of data per node can be assumed to be the size of the
In this example, we assume that this is 2 GB. The
parameter represents the amount of data to be checkpointed per unit time—however, this parameter is
actually expressed as the number of 8K memory pages to be checkpointed per 100 milliseconds. 2 GB
per 300 seconds is approximately 6.8 MB per second, or 700 KB per 100 milliseconds, which works out
to roughly 85 pages per 100 milliseconds.
Similarly, we can calculate
local checkpoints and the amount of memory required for indexes—that is, the IndexMemory.
Assuming that we permit 512 MB for indexes, this works out to approximately 20 8-KB pages per 100
milliseconds for this parameter.
Next, we need to determine the number of REDO log files required—that is, fragment log files—the
corresponding parameter being NoOfFragmentLogFiles. We need to make sure that there are
sufficient REDO log files for keeping records for at least 3 local checkpoints. In a production setting,
MySQL Cluster Configuration Files
Type/Units
boolean
Logging and Checkpointing
that are used to configure local checkpoints for a MySQL Cluster do not exist in
run by the application affects the values of 5 columns.
values are inserted by the application.
NoOfDiskPagesToDiskAfterRestartACC
Default
false
and in Data Memory, Index Memory, and
NoOfDiskPagesToDiskAfterRestartTUP
1592
Range/Values
true, false
is enabled,
Checksum
parameter.
DataMemory
in terms of the time for