Querying this table provides information similar to that
provided by the ALL REPORT
MemoryUsage command in the ndb_mgm
client, or logged by ALL DUMP
1000.
The following table provides information about the columns in
the memoryusage table. For each column, the
table shows the name, data type, and a brief description.
Additional information can be found in the notes following the
table.
| Column Name | Type | Description |
|---|---|---|
node_id | integer | The node ID of this data node. |
memory_type | string | One of Data memory or Index
memory, or (NDB 7.2.16 and
later) Long message
buffer. |
used | integer | Number of bytes currently used for data memory or index memory by this data node. |
used_pages | integer | Number of pages currently used for data memory or index memory by this data node; see text. |
total | integer | Total number of bytes of data memory or index memory available for this data node; see text. |
total_pages | integer | Total number of memory pages available for data memory or index memory on this data node; see text. |
The total column represents the total amount
of memory in bytes available for the given resource (data memory
or index memory) on a particular data node. This number should
be approximately equal to the setting of the corresponding
configuration parameter in the config.ini
file.
Suppose that the cluster has 2 data nodes having node IDs
5 and 6, and the
config.ini file contains the following:
[ndbd default] DataMemory = 1G IndexMemory = 1G
Suppose also that the value of the
LongMessageBuffer
configuration parameter is allowed to assume its default (64 MB
in NDB 7.2.16 and later).
The following query shows approximately the same values:
mysql> SELECT node_id, memory_type, total
> FROM ndbinfo.memoryusage;
+---------+---------------------+------------+
| node_id | memory_type | total |
+---------+---------------------+------------+
| 5 | Data memory | 1073741824 |
| 5 | Index memory | 1074003968 |
| 5 | Long message buffer | 67108864 |
| 6 | Data memory | 1073741824 |
| 6 | Index memory | 1074003968 |
| 6 | Long message buffer | 67108864 |
+---------+---------------------+------------+
6 rows in set (0.00 sec)
In this case, the total column values for
index memory are slightly higher than the value set of
IndexMemory due to
internal rounding.
For the used_pages and
total_pages columns, resources are measured
in pages, which are 32K in size for
DataMemory and 8K for
IndexMemory. For long
message buffer memory, the page size is 256 bytes.
Long message buffer information can be found in this table beginning with NDB 7.2.16; in earlier versions of NDB Cluster 7.2, only data memory and index memory were included.