For initial starts and system restarts this phase means executing a local checkpoint. This is handled by the master so that the other nodes will return immediately from this phase. Node restarts and initial node restarts perform the copying of the records from the primary replica to the starting replicas in this phase. Local checkpoints are enabled before the copying process is begun.
Copying the data to a starting node is part of the node takeover protocol. As part of this protocol, the node status of the starting node is updated; this is communicated using the global checkpoint protocol. Waiting for these events to take place ensures that the new node status is communicated to all nodes and their system files.
After the node's status has been communicated, all nodes are
signaled that we are about to start the takeover protocol for
this node. Part of this protocol consists of Steps 3 - 9 during
the system restart phase as described below. This means that
restoration of all the fragments, preparation for execution of
the redo log, execution of the redo log, and finally reporting
DBDIH when the execution of the redo
log is completed, are all part of this process.
After preparations are complete, copy phase for each fragment in the node must be performed. The process of copying a fragment involves the following steps:
DBLQH kernel block in the starting
node is informed that the copy process is about to begin by
sending it a
DBLQH acknowledges this request a
CREATE_FRAGREQ signal is sent to all
nodes notify them of the preparation being made to copy data
to this replica for this table fragment.
After all nodes have acknowledged this, a
COPY_FRAGREQ signal is sent to the node
from which the data is to be copied to the new node. This is
always the primary replica of the fragment. The node
indicated copies all the data over to the starting node in
response to this message.
After copying has been completed, and a
COPY_FRAGCONF message is sent, all nodes
are notified of the completion through an
After all nodes have updated to reflect the new state of the
DBLQH kernel block of the
starting node is informed of the fact that the copy has been
completed, and that the replica is now up-to-date and any
failures should now be treated as real failures.
The new replica is transformed into a primary replica if this is the role it had when the table was created.
After completing this change another round of
CREATE_FRAGREQ messages is sent to all
nodes informing them that the takeover of the fragment is
After this, process is repeated with the next fragment if another one exists.
When there are no more fragments for takeover by the node,
all nodes are informed of this by sending an
UPDATE_TOREQ signal sent to all of them.
Wait for the next complete local checkpoint to occur, running from start to finish.
The node states are updated, using a complete global checkpoint. As with the local checkpoint in the previous step, the global checkpoint must be permitted to start and then to finish.
When the global checkpoint has completed, it will
communicate the successful local checkpoint of this node
restart by sending an
END_TOREQ signal to
START_COPYCONF is sent back to the
starting node informing it that the node restart has been
START_COPYCONF signal ends
NDB_STTOR phase 5. This provides another
synchronization point for system restarts, designated as
The copy process in this phase can in theory be performed in parallel by several nodes. However, all messages from the master to all nodes are currently sent to single node at a time, but can be made completely parallel. This is likely to be done in the not too distant future.
In an initial and an initial node restart, the
SUMA block requests the subscriptions from
SUMA master node.
phase 6. No other
NDBCNTR activity takes