The NCK segment is used to allow the various applications on the network to synchronize their system clocks (system date and time).

Usage Notes: If this message is to be used to automatically reset/correct system clocks, it is recommended that the system or administrative personnel initiating the NMQ with the NCK segment have the authority to correct the clock (system date and time) for the other systems on the network. This is important in order to avoid the obvious confusion of multiple systems attempting to resynchronize each other's clocks.

If this message is used only to gather information on the various systems' clocks, it is still important for an administrative procedure to be worked out to avoid conflicts when resetting clocks.

HL7 Attribute Table - NCK - System Clock Segment

Seq#	DataElement	Description	Must Implement	Flags	Cardinality	Length	C.LEN	Vocabulary	DataType
NCK
1	01172	System Date/Time	SHALL		[1..1]	[4..24]			DTM

Definition: This field contains an HL7 time stamp. It is strongly recommended that seconds be included. If the message contains an NST or NSC segment, the NCK segment is optional. If the NCK segment is present, this field is required. If present in the NMQ message, or the unsolicited NMD message, it contains the system date/time of the sending system. If present in the NMR response message, it contains the responding system's date/time.

The NSC segment is used to inform (NMR query response) or announce (NMD unsolicited update) the start-up, shut-down, and/or migration (to a different CPU or file-server/file-system) of a particular application.

Usage Notes: Fields 2-9. These are not applicable ("n/a") when the type of change being requested or reported is start-up or shut-down. If the change is of type "M", at least one of fields 2-5 must be different from its corresponding field in range 6-9.

Fields 4-5, 8-9. See definitions for the MSH, message header segment, in Chapter 2, "Control Section," for fields 3-4, for system and facility. "Application" is available for interfacing with lower level protocols. "Facility" is entirely site-defined.

Fields 2-3, 6-7: entirely site-defined.

HL7 Attribute Table - NSC - Application Status Change Segment

Seq#	DataElement	Description	Must Implement	Flags	Cardinality	Length	C.LEN	Vocabulary	DataType
NSC
1	01188	Application Change Type	SHALL		[1..1]			0409 Application Change Type	CWE
2	01189	Current CPU			[0..1]				ST
3	01190	Current Fileserver			[0..1]				ST
4	01191	Current Application			[0..1]			0361	HD
5	01192	Current Facility			[0..1]			0362	HD
6	01193	New CPU			[0..1]				ST
7	01194	New Fileserver			[0..1]				ST
8	01195	New Application			[0..1]			0361	HD
9	01196	New Facility			[0..1]			0362	HD

Definition: This field contains the type of change being requested (if NMR query) or announced (if NMD unsolicited update). Refer to User-Defined Table 0409 - Application Change Type in Chapter 2C, Code Tables, for suggested values. It is assumed that "new" version starts up with no loss or duplication of data as old one is shutting down (if possible).

Definition: This field contains a site-specific name for the current CPU.

Definition: This field contains a site-specific name for the current fileserver or file system used by this application.

Definition: This field contains a site-specific name used to identify the "current" application process for interfacing with lower level protocols. To be used in conjunction with the sending/receiving system and facility values in the MSH. Entirely site-defined. User-defined Table 0361-Sending/Receiving Application is used as the user-defined table of values for the first component.

Definition: This field contains a site-specific name for the current facility used by this application. To be used in conjunction with the values for the sending/receiving system and facility values in the MSH. This field further describes the current application, NSC-5 Current Application. With the promotion of this field to an HD data type, the usage has been broadened to include not just the current facility but other organizational entities, such as: a) the organizational entity responsible for current application; b) the responsible unit; c) a product or vendor's identifier, etc. Entirely site-defined. User-defined Table 0362 – Sending/Receiving Facility is used as the HL7 identifier for the user-defined table of values for the first component.

Definition: This field contains a site-specific name for the new CPU.

Definition: This field contains a site-specific name for the new fileserver or file system used by this application.

Definition: This field contains a site-specific name used to identify "new" application processes for interfacing with lower level protocols. To be used in conjunction with the sending/receiving system and facility values in the MSH. Entirely site-defined. User-defined Table 0361-Sending/Receiving Application is used as the user-defined table of values for the first component.

Definition: This field contains a site-specific name for the new facility used by this application. To be used in conjunction with the values for the sending/receiving system and facility values in the MSH.

This field further describes the new application, NSC-8 New Application. With the promotion of this field to an HD data type, the usage has been broadened to include not just the new facility but other organizational entities, such as: a) the organizational entity responsible for new application; b) the responsible unit; c) a product or vendor's identifier, etc. Entirely site-defined. User-defined Table 0362 – Sending/Receiving Facility is used as the HL7 identifier for the user-defined table of values for the first component.

The NST segment allows application control-level statistical information to be passed between the various systems on the network. Some fields in this segment refer to portions of lower level protocols; they contain information that can be used by application management applications monitoring the state of various network links.

Usage Notes: Fields 2-15. These are all marked optional since the statistics kept on a particular link and negotiated between the two systems in question will vary. Not all values will apply to each system. Some values are concerned with the type of port, and some values pertain to the lower level protocol.

HL7 Attribute Table - NST - Application Control-Level Statistics Segment

Seq#	DataElement	Description	Must Implement	Flags	Cardinality	Length	C.LEN	Vocabulary	DataType
NST
1	01173	Statistics Available	SHALL		[1..1]	[1..1]		0136 Yes/no Indicator	ID
2	01174	Source Identifier			[0..1]				ST
3	01175	Source Type			[0..1]			0332 Source Type	ID
4	01176	Statistics Start			[0..1]				DTM
5	01177	Statistics End			[0..1]				DTM
6	01178	Receive Character Count			[0..1]				NM
7	01179	Send Character Count			[0..1]				NM
8	01180	Messages Received			[0..1]				NM
9	01181	Messages Sent			[0..1]				NM
10	01182	Checksum Errors Received			[0..1]				NM
11	01183	Length Errors Received			[0..1]				NM
12	01184	Other Errors Received			[0..1]				NM
13	01185	Connect Timeouts			[0..1]				NM
14	01186	Receive Timeouts			[0..1]				NM
15	01187	Application control-level Errors			[0..1]				NM

Definition: This field indicates the availability of statistics. Refer to HL7 Table 0136 - Yes/no Indicator for valid values.

N - the responding application does not keep any statistics. If the value "N" is specified, the response message is used to signify to the initiating application that the communication link between the initiating application and the responding application is operational (and fields 2-15 are empty in the response message).

Y - the responding application does keep statistics, fields 4 and 5 are required (and the response message contains one or more not empty or not unvalued fields in the range 2-3, 6-15).

Definition: This field identifies a particular lower level link (e.g., a port number).

Definition: This field identifies (in certain systems) whether a lower level source identifier is an initiate or accept type. Refer to HL7 Table 0332 – Source Type in Chapter 2C, Code Tables, for valid values.

Definition: This field contains the date/time stamp of the start of the collection of the statistics reported in fields 6-15 of this segment. It is strongly recommended that this value include seconds.

Definition: This field contains the date/time stamp of the end of the statistics collection period reported in fields 6-15 of this segment. It is strongly recommended that this value include seconds.

Definition: This field contains the number of characters received.

Definition: This field contains the number of characters sent.

Definition: This field contains the number of messages received.

Definition: This field contains the number of messages sent.

Definition: This field contains the number of messages received with checksum errors.

Definition: This field contains the number of messages received with length errors.

Definition: This field contains the number of "other" invalid messages received (excluding length and checksum errors).

Definition: This field contains the number of connect timeout errors.

Definition: This field contains the number of timeouts while waiting for a response to an initiated message.

Definition: This field contains the number of application control-level errors in response to an initiated message.