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17.5.8.7 The ndbinfo nodes Table »
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17.5.8.6. 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 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 Remarks
node_id integer The ID of this data node.
memory_type string One of DATA_MEMORY or INDEX_MEMORY
used integer Number of memory pages used; see text.
max integer Total number of memory pages available; see text.

For the used and max columns, resources are measured in pages, which are 16K in size for DataMemory and 8K for IndexMemory. The next example shows how to use this information in obtaining totals for DataMemory, IndexMemory, or both. You can do this by summing across data nodes and table columns, like this: 

mysql> USE ndbinfo;
Database changed
mysql> SET @IPAGE := 8 * 1024;
Query OK, 0 rows affected (0.03 sec)

mysql> SET @DPAGE := 2 * @IPAGE;
Query OK, 0 rows affected (0.00 sec)

mysql> SELECT
    ->     @DPAGE * SUM(used) as 'Total DataMemory Used',
    ->     @DPAGE * SUM(max) as 'Total DataMemory Available',
    ->     @DPAGE * SUM(used) DIV COUNT(*) as 'Average DataMemory Used Per Node',
    ->     @DPAGE * SUM(max) DIV COUNT(*) as 'Average DataMemory Available Per Node'
    ->         FROM memoryusage WHERE memory_type = 'DATA_MEMORY'\G
*************************** 1. row ***************************
                Total DataMemory Used: 106102784
           Total DataMemory Available: 209977344
     Average DataMemory Used Per Node: 53051392
Average DataMemory Available Per Node: 104988672
1 row in set (0.34 sec)

mysql> SELECT
    ->     @IPAGE * SUM(used) as 'Total IndexMemory Used',
    ->     @IPAGE * SUM(max) as 'Total IndexMemory Available',
    ->     @IPAGE * SUM(used) DIV COUNT(*) as 'Average IndexMemory Used Per Node',
    ->     @IPAGE * SUM(max) DIV COUNT(*) as 'Average IndexMemory Available Per Node'
    ->     FROM memoryusage WHERE memory_type = 'INDEX_MEMORY'\G
*************************** 1. row ***************************
                Total IndexMemory Used: 376832
           Total IndexMemory Available: 210239488
     Average IndexMemory Used Per Node: 188416
Average IndexMemory Available Per Node: 105119744
1 row in set (0.33 sec)

(We use DIV rather than / in both queries so that the results in all of the output columns are integers.)

Prior to MySQL Cluster NDB 7.1.2, the memory_type column was named DATA_MEMORY. (Bug#50926)