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DATA4

DATA4: TvxClientDataSet

Example​

procedure ScriptEvent(var Value: variant);
begin
  CreateData(DATA4, ['Code,string,40', 'Quantity,integer']);
  DATA4.Append;
  DATA4['Code'].AsString := 'SAMPLE-004';
  DATA4['Quantity'].AsInteger := 4;
  DATA4.Post;
  Value := DATA4.RecordCount;
end;

Usage​

DATA4 provides the fourth independent action-owned client dataset for general script working data.

Behaviour, errors and limits

  • Field values, cursor, filters, indexes and edit state are shared with subsequent code using DATA4 during the action.
  • Reusing it for another query/schema replaces prior assumptions and can invalidate field references.
  • Missing fields and invalid dataset state can raise; Data helper boundaries typically log/swallow their own errors and may leave it inactive.
  • In-memory Post does not prove database persistence or transaction commit.
  • Complete result materialisation can be expensive, and the mutable cursor is not thread-safe.
  • SQL/file helper calls have real external side effects; merely reading the variable does not.

The retained connection/command metadata can change between helper calls even though normal result browsing is detached. Always initialise DATA4 for the current role instead of relying on stale state.

Additional Technical Info​

DATA4 is the fourth general-purpose TvxClientDataSet owned by the active action. It is independent of every other Data variable and has no automatic schema, database table or persistence rule.

Velox constructs TvxActionMan.FData4, assigns its diagnostic name DATA4, and binds the instance to the script. The object is initially inactive and empty of field definitions; a script must explicitly create/load/query it.

Implementation and lifecycle

The Velox client dataset preserves string whitespace, disables auto-calculated fields and fetch-on-demand, and requests all provider records. A default SQL open copies data into memory, disables constraints/change logging, detaches the provider and closes the server dataset. Action cleanup later closes DATA4; scripts do not own or free it.

Related entries

External references

Created 2026-07-15