The tc_time_track_stats table provides time-tracking information obtained from the DBTC block (TC) instances in the data nodes, through API nodes access NDB. Each TC instance tracks latencies for a set of activities it undertakes on behalf of API nodes or other data nodes; these activities include transactions, transaction errors, key reads, key writes, unique index operations, failed key operations of any type, scans, failed scans, fragment scans, and failed fragment scans.
A set of counters is maintained for each activity, each counter covering a range of latencies less than or equal to an upper bound. At the conclusion of each activity, its latency is determined and the appropriate counter incremented. tc_time_track_stats presents this information as rows, with a row for each instance of the following:
Data node, using its ID
TC block instance
Other communicating data node or API node, using its ID
Upper bound value
Each row contains a value for each activity type. This is the number of times that this activity occurred with a latency within the range specified by the row (that is, where the latency does not exceed the upper bound).
The tc_time_track_stats table contains the following columns:
node_id
Requesting node ID
block_number
TC block number
block_instance
TC block instance number
comm_node_id
Node ID of communicating API or data node
upper_bound
Upper bound of interval (in microseconds)
scans
Based on duration of successful scans from opening to closing, tracked against the API or data nodes requesting them.
scan_errors
Based on duration of failed scans from opening to closing, tracked against the API or data nodes requesting them.
scan_fragments
Based on duration of successful fragment scans from opening to closing, tracked against the data nodes executing them
scan_fragment_errors
Based on duration of failed fragment scans from opening to closing, tracked against the data nodes executing them
transactions
Based on duration of successful transactions from beginning until sending of commit ACK, tracked against the API or data nodes requesting them. Stateless transactions are not included.
transaction_errors
Based on duration of failing transactions from start to point of failure, tracked against the API or data nodes requesting them.
read_key_ops
Based on duration of successful primary key reads with locks. Tracked against both the API or data node requesting them and the data node executing them.
write_key_ops
Based on duration of successful primary key writes, tracked against both the API or data node requesting them and the data node executing them.
index_key_ops
Based on duration of successful unique index key operations, tracked against both the API or data node requesting them and the data node executing reads of base tables.
key_op_errors
Based on duration of all unsuccessful key read or write operations, tracked against both the API or data node requesting them and the data node executing them.
The block_instance column provides the DBTC kernel block instance number. You can use this together with the block name to obtain information about specific threads from the threadblocks table.