This block provides data distribution (partitioning) management
services. It is responsible for maintaining data fragments and
replicas, handling of local and global checkpoints; it also
manages node and system restarts. It contains the following
files, all found in the directory
storage/ndb/src/kernel/blocks/dbdih:
Dbdih.hpp: This file contains the
definition of the Dbdih class, as well as
the FileRecordPtr type, which is used to
keep storage information about a fragment and its replicas.
If a fragment has more than one backup replica, then a list
of the additional ones is attached to this record. This
record also stores the status of the fragment, and is
64-byte aligned.
DbdihMain.cpp: Contains definitions of
Dbdih class methods.
printSysfile/printSysfile.cpp: Older
version of the printSysfile.cpp in the
main dbdih directory.
DbdihInit.cpp: Initializes
Dbdih data and records; also contains the
class destructor.
LCP.txt: Contains developer notes about
the exchange of messages between DIH and
LQH that takes place during a local
checkpoint.
Sysfile.hpp: Contains the definition of
the Sysfile structure; in other words,
the format of an NDB system file. See
Section 8.1, “MySQL Cluster File Systems”, for more
information about NDB system files.
This block often makes use of BACKUP blocks
on the data nodes to accomplish distributed tasks, such as
global checkpoints and system restarts.
This block is implemented as the Dbdih class,
whose definition may be found in the file
storage/ndb/src/kernel/blocks/dbdih/Dbdih.hpp.
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