ndbinfo: The NDB Cluster Information Database The counter’s internal ID number; normally an integer between 1 and 10, inclusive. The name of the counter. See text for names of individual counters and the NDB kernel block with which each counter is associated. The counter’s value Each counter is associated with a particular NDB kernel block. The  OPERATIONS  counter is associated with the  DBLQH  (local query handler) kernel block. A primary-key read counts as one operation, as does a primary-key update. For reads, there is one operation in  DBLQH per operation in  DBTC . For writes, there is one operation counted per fragment replica. The  ATTRINFO ,  TRANSACTIONS ,  COMMITS ,  READS ,  LOCAL_READS ,  SIMPLE_READS ,  WRITES , LOCAL_WRITES ,  ABORTS ,  TABLE_SCANS , and  RANGE_SCANS  counters are associated with the  DBTC (transaction co-ordinator) kernel block. LOCAL_WRITES  and  LOCAL_READS  are primary-key operations using a transaction coordinator in a node that also holds the primary fragment replica of the record. The  READS  counter includes all reads.  LOCAL_READS  includes only those reads of the primary fragment replica on the same node as this transaction coordinator.  SIMPLE_READS  includes only those reads in which the read operation is the beginning and ending operation for a given transaction. Simple reads do not hold locks but are part of a transaction, in that they observe uncommitted changes made by the transaction containing them but not of any other uncommitted transactions. Such reads are “simple”  from the point of view of the TC block; since they hold no locks they are not durable, and once  DBTC  has routed them to the relevant LQH block, it holds no state for them. ATTRINFO  keeps a count of the number of times an interpreted program is sent to the data node. See NDB Protocol Messages, for more information about  ATTRINFO  messages in the  NDB  kernel. The  block_name  and  block_instance  columns provide, respectively, the applicable NDB kernel block name and instance number. You can use these to obtain information about specific threads from the threadblocks  table. A number of counters provide information about transporter overload and send buffer sizing when troubleshooting such issues. For each LQH instance, there is one instance of each counter in the following list: • LQHKEY_OVERLOAD : Number of primary key requests rejected at the LQH block instance due to transporter overload • LQHKEY_OVERLOAD_TC : Count of instances of  LQHKEY_OVERLOAD  where the TC node transporter was overloaded • counter_name • val Notes The  LOCAL_TABLE_SCANS_SENT ,  READS_RECEIVED ,  PRUNED_RANGE_SCANS_RECEIVED , RANGE_SCANS_RECEIVED ,  LOCAL_READS_SENT ,  CONST_PRUNED_RANGE_SCANS_RECEIVED , LOCAL_RANGE_SCANS_SENT ,  REMOTE_READS_SENT ,  REMOTE_RANGE_SCANS_SENT , READS_NOT_FOUND ,  SCAN_BATCHES_RETURNED ,  TABLE_SCANS_RECEIVED , and SCAN_ROWS_RETURNED  counters are associated with the  DBSPJ  (select push-down join) kernel block. 4536