Ext.define('Calc.view.Main', {
     extend: 'Ext.panel.Panel'
	,alias:'widget.main'
	,requires:['Calc.view.MainModel','Calc.view.MainController']
	,controller:'main'
	,viewModel:{type:'main'	}
    ,layout: {type: 'hbox'}
    ,items: [{
		xtype: 'panel',
		region: 'center', 
		width: '100%',
		height: '100%',
		layout: 'accordion',
		items: [{
			xtype: 'dataform',
			title: '<center><b>Анкета</b></center>',
			listeners: {
                beforeExpand : function(form){
					var rec = Ext.StoreMgr.lookup("datastore").getAt(0);
                    form.loadRecord(rec);
                }
            }
		}
...........

var DtStore = Ext.create('Calc.store.dataStore');

Ext.define('Calc.view.DataForm', {
	 extend:'Ext.panel.Panel'
    ,alias:'widget.dataform'
    ,requires: ['Ext.form.field.Text']
	,id:'dataform'
    ,initComponent: function(){
        Ext.apply(this, {
            activeRecord: null,
            iconCls: 'icon-user',
            frame: true,
            defaultType: 'textfield',
            bodyPadding: 5,
            fieldDefaults: {
                anchor: '100%',
                labelAlign: 'right'
            },
            items: [{
		xtype: 'textfield',
		fieldLabel: 'Фамилия',
		labelAlign: 'left',
		cls: 'row-pnf-style',
		flex: 1,
		name:'l_lname'
	}],
            dockedItems: [{
                xtype: 'toolbar',
                dock: 'bottom',
                ui: 'footer',
                items: ['->', {
                    iconCls: 'icon-save',
                    itemId: 'save',
                    text: 'Save',
                    disabled: true,
                    scope: this,
                    handler: this.onSave
                }, {
                    iconCls: 'icon-reset',
                    text: 'Reset',
                    scope: this,
                    handler: this.onReset
                }]
            }]
        });
        this.callParent();
    },

    setActiveRecord: function(record){
		var record = DtStore.getAt(0);
        this.activeRecord = record;
        if (record) {
            this.down('#save').enable();
            this.getForm().loadRecord(record);
        } else {
            this.down('#save').disable();
            this.getForm().reset();
        }
    },

    onSave: function(){
        var active = this.activeRecord,
            form = this.getForm();

        if (!active) {
            return;
        }
        if (form.isValid()) {
            form.updateRecord(active);
            this.onReset();
        }
    },

    onReset: function(){
        this.setActiveRecord(null);
        this.getForm().reset();
    }
});

Ext.define('Calc.model.dataModel', {
    extend: 'Ext.data.Model',
	idProperty: 'l_id', 
	fields: [
		{name: 'l_id', type: 'int'},
		{name: 'l_lname',	type: 'string'},
		{name: 'l_drog_dt',type: 'date'},
		{name: 'l_sex',	type: 'string'}
	]
});

Ext.define('Calc.store.dataStore',{
	 extend:'Ext.data.JsonStore'
	,model:'Calc.model.dataModel'
	,alias:'store.datastore'
	,id:'datastore'
	,autoLoad: false
    ,buffered: false
	,proxy: {
		 type: 'ajax'
		,api:{
			 read:'/resources/jsn_rdata.php?act=read'
			,update:'/resources/jsn_rdata.php?act=update'
		}
		,reader: {
			type: "json" //json
		}
		,writer: {
			type: "json" //json
			,writeAllFields:true
		}
	}
});

listeners: {
                beforeExpand : function(form){
                    form.setActiveRecord();
                }

extend:'Ext.panel.Panel'  -> а нужно -> extend:'Ext.form.Panel'
.....
    ,initComponent: function(){
        Ext.apply(this, {
            activeRecord: null,
			HistDtStore:Ext.create('Calc.store.dataStore'),  //добавил сюда store
...
    setActiveRecord: function(){
		var record = this.HistDtStore.getAt(0);
        this.activeRecord = record;
        if (record) {
            this.down('#save').enable();
            this.getForm().loadRecord(record);
        } else {
            this.down('#save').disable();
            this.getForm().reset();
        }
    },
...
    onSave: function(){
        var active = this.activeRecord,
            form = this.getForm();

        if (!active) {
            return;
        }
        if (form.isValid()) {
			var values = this.getValues();
            this.HistDtStore.getAt(0).set(values);
			this.HistDtStore.save();
            form.updateRecord(active);
            this.onReset();
        }else{
		  alert('Не все обязательные поля заполнено правильно!');
		}
    }

extend:'Ext.data.JsonStore' -> а нужно -> extend:'Ext.data.Store'