MySQL Cluster Tutorial - cdn.oreillystatic.com

The counter_name indicates what events are being counted and the val field provides the
current count (since the last restart for the node).
This information can be used to understand how an application’s SQL queries (or NDB API
method calls) are mapped into data node operations and can be invaluable when tuning
the database and application.
ndbinfo.logbuffers
This view presents information on the size of the redo and undo log buffers as well as how
much of that space is being used:
mysql> select * from ndbinfo.logbuffers;
+---------+----------+--------+----------+----------+--------+
| node_id | log_type | log_id | log_part | total | used |
+---------+----------+--------+----------+----------+--------+
| 3 | REDO | 0 | 1 | 67108864 | 131072 |
| 3 | REDO | 0 | 2 | 67108864 | 131072 |
| 3 | DD-UNDO | 4 | 0 | 2096128 | 0 |
| 4 | REDO | 0 | 1 | 67108864 | 131072 |
| 4 | REDO | 0 | 2 | 67108864 | 131072 |
| 4 | DD-UNDO | 4 | 0 | 2096128 | 0 |
+---------+----------+--------+----------+----------+--------+
This information can be used to identify when the buffers are almost full so that the
administrator can increase their size – preempting potential issues. If the redo log buffers
are exhausted then applications will see 1221 “REDO log buffers overloaded” errors. In
extreme cases, if the undo log buffers fill too quickly then the database may be halted.
When using the multi-threaded data node (ndbmtd), the log_part column is used to
distinguish between different LQH threads.
The sizes of the redo buffer can be increased using the RedoBuffer parameter. The size of
the undo buffer is specified in the undo_buffer_size attribute when creating the log file.
ndbinfo.logspaces
This view provides information on the disk space that has been configured for the log spaces for
redo and undo logs:
mysql> select * from logspaces;
+---------+----------+--------+----------+-----------+--------+
| node_id | log_type | log_id | log_part | total | used |
+---------+----------+--------+----------+-----------+--------+
| 3 | REDO | 0 | 0 | 536870912 | 0 |
| 3 | REDO | 0 | 1 | 536870912 | 0 |
| 3 | REDO | 0 | 2 | 536870912 | 0 |
| 3 | REDO | 0 | 3 | 536870912 | 0 |
| 3 | DD-UNDO | 4 | 0 | 78643200 | 169408 |
| 4 | REDO | 0 | 0 | 536870912 | 0 |
| 4 | REDO | 0 | 1 | 536870912 | 0 |
| 4 | REDO | 0 | 2 | 536870912 | 0 |
| 4 | REDO | 0 | 3 | 536870912 | 0 |
| 4 | DD-UNDO | 4 | 0 | 78643200 | 169408 |
+---------+----------+--------+----------+-----------+--------+
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