## Notes 

• lock_num 

ID of lock object 

• waiting_for 

Waiting for lock with this ID 

The table ID ( tableid  column) is assigned internally, and is the same as that used in other ndbinfo tables. It is also shown in the output of ndb_show_tables . 

The transaction ID ( transid  column) is the identifier generated by the NDB API for the transaction requesting or holding the current lock. 

The mode  column shows the lock mode; this is always one of S  (indicating a shared lock) or X  (an exclusive lock). If a transaction holds an exclusive lock on a given row, all other locks on that row have the same transaction ID. 

The state  column shows the lock state. Its value is always one of H  (holding) or W  (waiting). A waiting lock request waits for a lock held by a different transaction. 

When the detail  column contains a *  (asterisk character), this means that this lock is the first holding lock in the affected row’s lock queue; otherwise, this column is empty. This information can be used to help identify the unique entries in a list of lock requests. 

The op  column shows the type of operation requesting the lock. This is always one of the values READ , INSERT , UPDATE , DELETE , SCAN , or REFRESH . 

The duration_millis  column shows the number of milliseconds for which this lock request has been waiting or holding the lock. This is reset to 0 when a lock is granted for a waiting request. 

The lock ID ( lockid  column) is unique to this node and block instance. 

The lock state is shown in the lock_state  column; if this is W , the lock is waiting to be granted, and the waiting_for  column shows the lock ID of the lock object this request is waiting for. Otherwise, the waiting_for  column is empty. waiting_for  can refer only to locks on the same row, as identified by node_id , block_instance , tableid , fragmentid , and rowid . 

## 23.5.14.6 The ndbinfo cluster_operations Table 

The cluster_operations  table provides a per-operation (stateful primary key op) view of all activity in the NDB Cluster from the point of view of the local data management (LQH) blocks (see The DBLQH Block). 

The cluster_operations  table contains the following columns: 

• node_id 

Node ID of reporting LQH block 

• block_instance 

LQH block instance 

• transid 

Transaction ID 

