CreateTags method (C++)

To create new history tags, use the following syntax in a C++ program:

HRESULT (
        [in] DWORD dwNumItems,
        [in, size_is(dwNumItems)] LPWSTR *pszTag,
        [in, size_is(dwNumItems)] int *pTagType,
        [out, size_is(,dwNumItems)] HRESULT **ppErrors);

Parameter	Description
`dwNumItems`	The number of history tags to be written to the DeltaV Continuous Historian database.
`pszTag`	An array of pointers to strings containing the path/tag names to be written to the DeltaV Continuous Historian database.
`pTagType`	An array of integers that define the history tag data types as either a float (2) or a string (3). Note To represent history tags of a different data type – such as Boolean or Named Set enumeration, for example – the client application that calls the CreateTags method must map them to either a float or string type.
`ppErrors`	An array of pointers to HRESULTs for each history tag creation operation.

Important

After creating a history tag using the CreateTags method, it cannot be deleted.

Rules and operation

The CreateTags method performs a security check to verify with the DeltaV runtime services that the user has the HISTORICAL_DATA_ENTRY key in DeltaV in order to create history tags. For applications running locally to the OPC HDA server, the user will be the interactive Windows user. For applications running remotely, a DCOM query is used to determine the user that made the call.⁽¹⁾

After user security is verified, the CreateTags method attempts to validate all .HDE tags passed according to the following rules:

Historical data is identified by the history tag string specified for a history sample. History tag strings must conform to the following syntax:
HDE_tag_prefix.HDE

The .HDE suffix distinguishes a history tag from a scanned data tag.

HDE_tag_prefix must conform to the following rules:
- Can be no more than 160 Unicode characters
- Can contain alphanumeric characters only
- Must include at least one alphabetic character (using the current DeltaV locale)
- Can contain no character that has a different code value if converted to upper case (using the current DeltaV locale)
- Can contain the following nonalphanumeric characters:⁽²⁾
  - Dollar sign ($) – 0x0024; decimal 0036
  - Hyphen (-) – 0x002D; decimal 0045
  - Slash mark (/) – 0x002F; decimal 0047
  - Left bracket ([) – 0x005B; decimal 0091
  - Right bracket (]) – 0x005D; decimal 0093
  - Underscore (_) – 0x005F; decimal 0095
Note

All history tags are converted to uppercase before being created in a data set.
The OPC write interface supports a maximum of 2,000 unique history tags with one or more history samples in the current and active historical data set.
Two or more history samples cannot have an identical history tag and time stamp.

⁽¹⁾ For more information about OPC Remote and DCOM setup, refer to the Using OPC and DCOM Setup topics in the Integration section of DeltaV Books Online.

⁽²⁾ On a Japanese DeltaV system, Unicode characters with the following hex code values are also treated as alphabetic characters: 0x3005, 0x309B, 0x309C, 0x309D, 0x309E, 0x30FC, 0x30FD, 0x30FE, 0xFF70, 0xFF9E, and 0xFF9F.