Access ODBC to SQL Server 'Connection busy with results from another command'

Instead DAO.Recordset use ADODB.Recordset? Also, try turning on MARS.

Using MARS from ODBC and OLE DB
To use MARS with ODBC the connection string addition is “MARS_Connection=yes”, or you can a connection attribute as follows:
    SQLSetConnectAttr(hdbc, SQL_COPT_SS_MARS_ENABLED,SQL_MARS_ENABLED_YES, SQL_IS_UINTEGER);
before calling SQLDriverConnect or SQLBrowseConnect. With OLE DB, the provider string addition for IDBInitialize::Initialize is “MarsConn=yes”, or “MARS Connection=true” if you use an initialization string with IDataInitialize::GetDataSource. You can also enable MARS programmatically as follows:

    IDBInitialize *pIDBInitialize = NULL;
    IDBProperties *pIDBProperties = NULL;
    // Create the data source object.
    hr = CoCreateInstance(CLSID_SQLNCLI, NULL, CLSCTX_INPROC_SERVER,IID_IDBInitialize, (void**)&pIDBInitialize);
    hr = pIDBInitialize->QueryInterface(IID_IDBProperties, (void**)&pIDBProperties);

    // Set the MARS property.
    DBPROP rgPropMARS;
    IDBProperties rgPropMARS.dwPropertyID = SSPROP_INIT_MARSCONNECTION;
    rgPropMARS.dwOptions = DBPROPOPTIONS_REQUIRED;
    rgPropMARS.dwStatus = DBPROPSTATUS_OK;
    rgPropMARS.colid = DB_NULLID;
    V_VT(&(rgPropMARS.vValue)) = VT_BOOL;
    V_BOOL(&(rgPropMARS.vValue)) = VARIANT_TRUE;

    // Create the structure containing the properties.
    DBPROPSET PropSet;
    PropSet.rgProperties = &rgPropMARS;
    PropSet.cProperties = 1;
    PropSet.guidPropertySet = DBPROPSET_SQLSERVERDBINIT;

    // Get an IDBProperties pointer and set the initialization properties.
    pIDBProperties->SetProperties(1, &PropSet);
    pIDBProperties->Release();
    // Initialize the data source object.
    hr = pIDBInitialize->Initialize();

"The subforms in question are very basic forms based on simple tables with no specific code involved so I cannot understand the issue."

"I have a main form with several sub-forms and after adding a further couple of sub-forms today,"

So your main form possibly contains more that 4 subforms?

Can you explain the purpose of this main form that it needs possibly over 4 subforms?
Are the subform related "vertically" (multiple Nested subforms), or horizontally (one man form and many subforms at the same level below the main form)

Typically you will have a main form and possibly two subforms, but not more than that because it can become confusing for the user (and the developer)
My theory here is the complexity of the form(s) may be contributing to the error (as I have never gotten this error in my multiform basic setups)

"I think I read somewhere previously that adding a timestamp field can help "
Yes, and also make sure to have a primary key in each table.

Finally, Access contains a few settings that you can use to manage possible "Timing" issues like this.
(see attached screenshot)


JeffCoachman
untitled.JPG

Well, bit of a long story, but the main form is not linked to any of the subforms.. it originally started life as a simple 'admin' form with a few subforms to view/edit some basic tables. I had a simple button interface to show / hide one subform at a time.
This has grown beyond it's original idea so I'll be looking to redesign, especially in light of odbc issues etc.

OK

Then first create the simple main form and test.
Then add one form at a time until the issuse appears.

"but the main form is not linked to any of the subforms.. it originally started life as a simple 'admin' form with a few subforms to view/edit some basic tables."
Then simply create one form for each table and use a "Menu form" to open each one individually.
  "Keep it simple"

;-)

JeffCoachman

If you build the individual forms, you can use the "switchboard manager" in access to create a "Menu" system.

Null field value seemed to be causing the error so I think we can close the question. Thanks for further help from everyone.