5.3 STTOR Phase 0

Most NDB kernel blocks begin their start phases at STTOR Phase 1, with the exception of NDBFS and NDBCNTR, which begin with Phase 0, as can be seen by inspecting the first value for each element in the ALL_BLOCKS array (defined in src/kernel/blocks/ndbcntr/NdbcntrMain.cpp). In addition, when the STTOR signal is sent to a block, the return signal STTORRY always contains a list of the start phases in which the block has an interest. Only in those start phases does the block actually receive a STTOR signal.

STTOR signals are sent out in the order in which the kernel blocks are listed in the ALL_BLOCKS array. While NDBCNTR goes through start phases 0 to 255, most of these are empty.

Both activities in Phase 0 have to do with initialization of the NDB file system. First, if necessary, NDBFS creates the file system directory for the data node. In the case of an initial start, NDBCNTR clears any existing files from the directory of the data node to ensure that the DBDIH block does not subsequently discover any system files (if DBDIH were to find any system files, it would not interpret the start correctly as an initial start).

Each time that NDBCNTR completes the sending of one start phase to all kernel blocks, it sends a NODE_STATE_REP signal to all blocks, which effectively updates the NodeState in all blocks.

Each time that NDBCNTR completes a nonempty start phase, it reports this to the management server; in most cases this is recorded in the cluster log.

Finally, after completing all start phases, NDBCNTR updates the node state in all blocks using a NODE_STATE_REP signal; it also sends an event report advising that all start phases are complete. In addition, all other cluster data nodes are notified that this node has completed all its start phases to ensure all nodes are aware of one another's state. Each data node sends a NODE_START_REP to all blocks; however, this is significant only for DBDIH, so that it knows when it can unlock the lock for schema changes on DBDICT.


In the following table, and throughout this text, we sometimes refer to STTOR start phases simply as start phases or Phase N (where N is some number). NDB_STTOR start phases are always qualified as such, and so referred to as NDB_STTOR start phases or NDB_STTOR phases.

Table 5.1 NDB kernel blocks and start phases

Kernel Block Receptive Start Phases
DBLQH 1, 4
NDBCNTR 0, 1, 2, 3, 4, 5, 6, 8, 9
CMVMI 1 (prior to QMGR), 3, 8
QMGR 1, 7
BACKUP 1, 3, 7
SUMA 1, 3, 5, 7, 100 (empty), 101
DBTUX 1,3,7
TSMAN 1, 3 (both ignored)
LGMAN 1, 2, 3, 4, 5, 6 (all ignored)
PGMAN 1, 3, 7 (Phase 7 currently empty)
RESTORE 1,3 (only in Phase 1 is any real work done)


This table was current at the time this text was written, but is likely to change over time. The latest information can be found in the source code.