[Ex_Soft]

Ext.Loader.setConfig({
	enabled: true,
	disableCaching: false,
	paths: {
		"Ext.ux": "../../../../../../../ExtJS/ExtJS4/ExtJS4.1.1a/examples/ux"
	}
});

Ext.require([
	"Ext.ux.data.PagingMemoryProxy"
]);

Ext.define("TestModel", {
    extend: "Ext.data.Model",
    idProperty: "id",
    fields: [
        { name: "id", type: "int" },
        { name: "name", type: "string" }
    ]
});

Ext.onReady(function() {
    var
        maxRecordsCount = 50000,
        pageSize = 150,
        createData = function(max) {
            var
                data = [];

            for(var i=0; i<max; ++i)
                data.push( [ i, "Record# "+i ] );

            return data;
        },
        data = createData(maxRecordsCount),
        store = Ext.create("Ext.data.ArrayStore", {
            model: "TestModel",
            pageSize: pageSize,
            proxy: {
                type: "pagingmemory",
                reader: {
                    type: "array"
                }
                //, data: data // need store.load() || store.loadPage()
            }
            //, data: data // store loads data automatically
        }),
        grid = Ext.create("Ext.grid.Panel", {
            store: store,
            columns: [
                { dataIndex: "id", header: "id" },
                { dataIndex: "name", header: "name" }
            ],
            selModel: {
                pruneRemoved: false
            },
            multiSelect: true,
            viewConfig: {
                trackOver: false
            },
            dockedItems: [{
                xtype: "pagingtoolbar",
                dock: "bottom",
                store: store,
                displayInfo: true
            }]
        });

    Ext.create("Ext.window.Window", {
        autoShow: true,
        layout: "fit",
        height: 400,
        width: 1100,
        maximizable: true,
        items: [grid]
    });

    store.getProxy().data = data;

    store.load();
    //store.loadPage(1);
});

P.S. Если Вы посмотрите исходники Ext.ux.data.PagingMemoryProxy (ExtJS/examples/ux/data/PagingMemoryProxy.js), то Вы увидите, что PagingMemoryProxy хранит ВСЕ данные в себе.