The DBLQH block initiates checking of the log files here. Then it obtains the states of the data nodes using the READ_NODESREQ signal. Unless an initial start or an initial node restart is being performed, the checking of log files is handled in parallel with a number of other start phases. For initial starts, the log files must be initialized; this can be a lengthy process and should have some progress status attached to it.

The DBDICT block requests information about the cluster data nodes via the READ_NODESREQ signal. DBACC resets the system restart flag if this is not a system restart; this is used only to verify that no requests are received from DBTUX during system restart. DBTC requests information about all nodes by means of the READ_NODESREQ signal.

DBDIH sets an internal master state and makes other preparations exclusive to initial starts. In the case of an initial start, the nonmaster nodes perform some initial tasks, the master node doing once all nonmaster nodes have reported that their tasks are completed. (This delay is actually unnecessary since there is no reason to wait while initializing the master node.)

For node restarts and initial node restarts no more work is done in this phase. For initial starts the work is done when all nodes have created the initial restart information and initialized the system file.

For system restarts this is where most of the work is performed, initiated by sending the NDB_STARTREQ signal from NDBCNTR to DBDIH in the master. This signal is sent when all nodes in the system restart have reached this point in the restart. This we can mark as our first synchronization point for system restarts, designated WAITPOINT_4_1.

For a description of the system restart version of Phase 4, see Section 6.5.21, “System Restart Handling in Phase 4”.

After completing execution of the NDB_STARTREQ signal, the master sends a CNTR_WAITREP signal with WAITPOINT_4_2 to all nodes. This ends NDB_STTOR phase 3 as well as (STTOR) Phase 4.