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A parser is a program that interprets the physical bit stream of an incoming message, and creates an internal logical representation of the message in a tree structure. The parser also regenerates a bit stream for an outgoing message from the internal message tree representation. A parser is called when the bit stream that represents an input message is converted to the internal form that can be handled by the broker; this invocation of the parser is known as parsing. The internal form, a logical tree structure, is described in Logical tree structure. It is described as a tree because messages are typically hierarchical in structure; a good example of this structure is XML. The way in which the parser interprets the bit stream is unique to that parser; therefore, the logical message tree that is created from the bit stream varies from parser to parser.

The parser that is called depends on the structure of a message, referred to as the message template. Message template information comprises the message domain, message set, message type, and physical format of the message. Together, these values identify the structure of the data that the message contains.

A parser is also called when a logical tree that represents an output message is converted into a bit stream; this action by the parser is known as writing. Typically, an output message is generated by an output node at the end of the message flow. However, you can connect more nodes to an output node to continue processing of the message.

The message domain identifies the parser that is used to parse and write instances of the message. The remaining parts of the message template, message set, message type, and physical format, are optional, and are used by model-driven parsers such as the MRM parser.

For each message flow parser type, this test reports the largest bit stream that is parsed/written. In addition, this test reports the processing rate of each parser type in terms of parses and writes. This way, administrators may be alerted to processing bottlenecks, if any.

Measurement	Description	Measurement Unit	Interpretation
threads	Indicates the number of message flow threads that contributed to the statistics of this message flow parser type accumulation during the last measurement period.	Number
memoryUtil	Indicates the approximate amount of user data-related memory used for this message flow parser type during the last measurement period.	KB	The value of this measure cannot be calculated exactly.
maxReadBitStream	Indicates the largest bit stream parsed by this message flow parser type during the last measurement period.	KB
maxWrittenBitStream	Indicates the largest bit stream written by this message flow parser type during the last measurement period.	KB
reads	Indicates the rate at which parses were completed successfully by this message flow parser type during the last measurement period.	Reads/sec	Comapring the value of this measure across the parser types will help you identify the parser type that is busy processing the parses.
failedReads	Indicates the rate at which parses failed in this message flow parser type during the last measurement period.	Reads/sec	A low value is desired for this measure. A sudden/gradual increase in the value of this measure indicates processing bottlenecks.
writes	Indicates the rate at which writes were completed successfully to this message flow parser type during the last measurement period.	Writes/sec	Comparing the value of this measure across the parser types will help you identify the parser type that is busy writing the messages.
failedWrites	Indicates the rate at which parses failed to be written to this message flow parser type during the last measurement period.	Writes/sec	A low value is desired for this measure. A sudden/gradual increase in the value of this measure indicates processing bottlenecks.