Reading the value of a specified historical value in the given time.

If the parameter archIdent is a reference to an object of Historical value type, the action performance is described above. If the parameter is a reference to an object (not of the Historical value type) or a structured variable item that is not of the Object type, the system will attempt to find an object of the Historical value type that archives values of the object (item).
If the parameter archIdent is a reference to a structured variable item that is of the Object type, the item "points" to an object in the system. If the object is of the Historical value type, the action will read data from it. If it is not, the system will attempt to find an object of the Historical value type that archives values of the object.

The result of reading (value) will be assigned to the variable valueIdent_Real.

If the identifier isDataIdent_Bool is specified, the action will assign it the following value:

• True - data was read,
• False - data is not available (or the data at the required time has the DELETED flag - it was deleted by the user).

If the identifier isDataIdent_Bool is not used and no data was read, the action doesn't modify the value of the identifier valueIdent_Real.

If periodic/statistical archives are read and timeExpression_TmA is not aligned to the calculation period and offset, the nearest older value is returned.
If periodic/statistical archives are read and timeExpression_TmA is newer than the time of the last calculated value, the reading will not return any data.

If the identifier archFlagsIdent_Int is specified, archive flags for a value, which were read, are saved into the identifier (archive flags are defined as the sum of the following constants):

• 1 - (ArcStart) - value stored into the database at the moment of the D2000 Archiv start
• 2 - (ArcStop) - value stored into the database at the moment of the D2000 Archiv stop
• 4 - (ArcBlock) - value stored into the database at the beginning of blocking of the archiving (by the stop condition of archiving configured in the D2000 CNF)
• 8 - (ArcUnBlock) - value stored into the database at the end of blocking of the archiving (by the start condition of archiving configured inthe  D2000 CNF)
• 16 - (ArcDeleted) - value from the archive database that was deleted by an user. The action ignores the deleted value (as if it were not in the archive)
• 32 - (ArcUsermodify) - value in the archive that was modified by an user
• 64 - (ArcOldVal) - old value that was read from a communication station
• 128 - (ArcProcessModify) - value that was modified by a process (not by an user: ESL Script, D2000 VBApi, ...)
• 256 (ArcLoadData) - obsolete: value was obtained from OS/2 database SQL Gupta via "On-line archive database import"
• 512 (ArcMonoTime) - value is stored with monotonous time
• 1024 (ArcK) - value of periodic archive is generated during reading as a copy of previous value

The logical AND (&), that may be also applied into integer operands, is used to test archive flags.
For example: If the condition archFlagsIdent_Int & 4 = 4 is true, then the flag of a value that was read from the archive database by means of the action GETARCHVAL is has ArcBlock flag (blocking of the archiving).

The value of the parameter archivInstance_Int defines the instance of archive which executes the request. If the parameter is not defined (or the value is 0), the active instance of archive will execute the request.

For versions newer than 21.0.70, you can specify a VALID or INVALID clause. This clause can be used to read the last valid (VALID) or invalid (INVALID) value for a given time (ignoring all following values which are not VALID or INVALID).

• If the particular archive process is not running, the action generates the error _ERR_ARCHIV_NOT_RUNNING.
• If an an object of the Historical value is archived:
  • periodically, reading a value out of the period is unsuccessful
  • according to a filter, value for the required time is to be derived from the last stored value in the archive.

Reading of archived value: