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18.5.14.16 The ndbinfo memoryusage Table

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 memoryusage table contains the following columns:

  • node_id

    The node ID of this data node.

  • memory_type

    One of Data memory, Index memory, or Long message buffer.

  • used

    Number of bytes currently used for data memory or index memory by this data node.

  • used_pages

    Number of pages currently used for data memory or index memory by this data node; see text.

  • total

    Total number of bytes of data memory or index memory available for this data node; see text.

  • total_pages

    Total number of memory pages available for data memory or index memory on this data node; see text.

Notes

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 7.3.5 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 7.3.5; in earlier versions of NDB Cluster, only data memory and index memory were included.