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The MySQL Cluster API Developer Guide :: 6 MySQL Cluster Internals :: 6.3 The NDB Protocol :: 6.3.2 Message Naming Conventions and Structure
6.3.3 Operations and Signals »
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6.3.2. Message Naming Conventions and Structure

This section describes the NDB Protocol message types and their structures.

Naming Conventions.  Message names are constructed according to a simple pattern which should be readily apparent from the discussion of request and response types in the previous section. These are shown in the following matrix:

Operation Type Request (REQ) Response/Success (CONF) Response/Failure (REF)
Primary Key Lookup (TCKEY) TCKEYREQ TCKEYCONF TCKEYREF
Unique Key Lookup (TCINDX) TCINDXREQ TCINDXCONF TCINDXREF
Table or Index Scan (SCANTAB) SCANTABREQ SCANTABCONF SCANTABREF
Result Retrieval (SCAN_NEXT) SCAN_NEXTREQ SCANTABCONF SCANTABREF
Transaction Record Acquisition (TCSEIZE) TCSEIZEREQ TCSEIZECONF TCSEIZEREF
Transaction Record Release (TCRELEASE) TCRELEASEREQ TCRELEASECONF TCRELEASEREF

CONF and REF are shorthand for “confirmed” and “refused”, respectively.

Three additional types of messages are used in some instances of inter-node communication. These message types are:

  1. A KEYINFO message contains information about the key used in a TCKEYREQ or TCINDXREQ message. It is employed when the key data does not fit within the request message. KEYINFO messages are also sent for index scan operations in which bounds are employed.

  2. An ATTRINFO message contains nonkey attribute values which does not fit within a TCKEYREQ, TCINDXREQ, or SCANTABREQ message. It is used for:

    • Supplying attribute values for inserts and updates

    • Designating which attributes are to be read for read operations

    • Specifying optional values to read for delete operations

  3. A TRANSID_AI message contains data returned from a read operation — in other words, it is a result set (or part of one).