Appendix A NDB Internals Glossary

This appendix contains terms and abbreviations that are found in or useful to understanding the NDB source code.

ACC.  ACCelerator or ACCess manager. Implemented as the DBACC kernel block, which handles hash indexes of primary keys, providing fast access to records.

API node.  In NDB terms, this is any application that accesses cluster data using the NDB API, including mysqld when functioning as an API node. (MySQL servers acting in this capacity are also referred to as “SQL nodes”.) Sometimes abbreviated informally as “API”. See NDB Cluster Nodes, Node Groups, Fragment Replicas, and Partitions.

BACKUP.  In the NDB kernel, the block having this name performs online backups and checkpoints. For more information, see Section 4.1, “The BACKUP Block”.

CMVMI.  Stands for Cluster Manager Virtual Machine Interface. An NDB kernel handling nonsignal requests to the operating system, as well as configuration management, interaction with the cluster management server, and interaction between various kernel blocks and the NDB virtual machine. See Section 4.2, “The CMVMI Block”, for more information.

CNTR.  Stands for restart CoordiNaToR. See Section 4.14, “The NDBCNTR Block”, for more information.

DBINFO.  The Database Information block provides support for the ndbinfo information database used to obtain information about data node internals. See Section 4.6, “The DBINFO Block”.

DBTC.  The transaction coordinator (also sometimes written simply as TC). See Section 4.9, “The DBTC Block”, for more information.

DICT.  The NDB data DICTionary kernel block. Also DBDICT. See Section 4.4, “The DBDICT Block”.

DIH.  DIstribution Handler. An NDB kernel block. See Section 4.5, “The DBDIH Block”.

LDM.  Local Data Manager. This set of NDB kernel blocks executes the code that manages the data handled on a given data node. It includes the DBTUP, DBACC, DBLQH, DBTUX, BACKUP, TSMAN, LGMAN, PGMAN, and RESTORE blocks.

Each such set of modules is referred to as an LDM instance, and is responsible for tuple storage, hash and T-tree indexes, page buffer and tablespace management, writing and restoring local checkpoints, and Disk Data log management. A data node can have multiple LDM instances, each of which can be distributed among a set of threads. Each LDM instance works with its own partition of the data.

LGMAN.  The Log Group MANager NDB kernel block, used for NDB Cluster Disk Data tables. See Section 4.13, “The LGMAN Block”.

LQH.  Local Query Handler. NDB kernel block, discussed in Section 4.7, “The DBLQH Block”.

MGM.  ManaGeMent node (or management server). Implemented as the ndb_mgmd server daemon. Responsible for passing cluster configuration information to data nodes and performing functions such as starting and stopping nodes. Accessed by the user by means of the cluster management client (ndb_mgm). A discussion of management nodes can be found in ndb_mgmd — The NDB Cluster Management Server Daemon.

NDB_STTOR.  NDB STarT Or Restart

QMGR.  The cluster management block in the NDB kernel. It responsibilities include monitoring heartbeats from data and API nodes. See Section 4.17, “The QMGR Block”, for more information.

RBR.  Row-Based Replication. NDB Cluster Replication is row-based replication. See NDB Cluster Replication.

STTOR.  STarT Or Restart

SUMA.  The cluster SUbscription MAnager. See Section 4.19, “The SUMA Block”.

TC.  Transaction Coordinator. See Section 4.9, “The DBTC Block”.

TRIX.  Stands for TRansactions and IndeXes, which are managed by the NDB kernel block having this name. See Section 4.23, “The TRIX Block”.

TSMAN.  Table space manager. Handles tablespaces for NDB Cluster Disk Data. See Section 4.22, “The TSMAN Block”, for more information.

TUP.  TUPle. Unit of data storage. Also used (along with DBTUP) to refer to the NDB kernel's tuple management block, which is discussed in Section 4.10, “The DBTUP Block”.