In Dynamics 365 Finance and Operations (D365 F&O), forms are the frontline of user interaction, but poor performance can turn them into bottlenecks—slow loads, UI freezes, and database contention frustrate users and tank productivity. Based on standard Microsoft practices and real-world developer discussions, this article breaks down four key optimization tips: judicious use of select forupdate, query indexing, minimizing client-side loops, and deferring non-essential data asynchronously. These aren't optional niceties; ignore them, and your forms will drag, especially in high-volume environments. We'll explain each with examples, assuming the latest online D365 F&O—no outdated hacks here.
Tip 1: Use select forupdate Only When Needed to Avoid Unnecessary Locks
Database locks from select forupdate are essential for transactional integrity during updates, but overusing it in read-heavy forms creates contention—other users or processes wait, leading to deadlocks and sluggish performance. Only apply it right before modifications in a TTS scope; for read-only operations like form loads or grids, skip it entirely to allow shared reads without blocking.
It's not about avoiding it altogether—it's necessary for safe inserts/updates/deletes to prevent runtime errors like mismatched TTS levels. But in forms, where most ops are display-only, default to plain select statements.
Example: In a form's button clicked method for updating a vendor record, use it sparingly within TTS. Don't lock during initial data fetch.
/**
* updateVendorStatus
* ----------------
* Updates the vendor status transactionally, applying forupdate only for the modification to minimize locks.
*
* September 22, 2025: Created by Jian Zhang for performance optimization article.
*/
public void updateVendorStatus(VendTable _vendTable, str _newStatus)
{
ttsbegin;
// Apply forupdate here, just before update
select forupdate _vendTable where _vendTable.AccountNum == this.AccountNum;
if (_vendTable)
{
_vendTable.Status = _newStatus;
_vendTable.update();
}
ttscommit;
}For a read-only grid in init(), use select VendTable;—no locks, faster multi-user access.
Tip 2: Optimize Queries by Adding Indexes on Underlying Tables
Form data sources execute queries against tables; without indexes on filtered, sorted, or joined fields, SQL resorts to full table scans, crippling load times on large datasets. You don't index data sources directly—add them to the underlying table (via extension for base tables like VendTable) so the query optimizer leverages them automatically.
For custom tables, add directly; for base, use extensions to stay upgrade-safe. Profile queries with tools like SQL Server Profiler to identify misses—bad ones turn quick forms into minutes-long waits.
Example: If your VendTable form filters by VendGroup frequently, add an index via table extension.
// In VendTable extension: Add index in VS designer
// Index: Fields = VendGroup; AllowDuplicates = Yes; Enabled = Yes;
// Then in form data source executeQuery for optimized filtering
/**
* executeQuery
* ----------------
* Executes the data source query with a custom range, relying on table indexes for efficiency.
*
* September 22, 2025: Created by Jian Zhang for performance optimization article.
*/
public void executeQuery()
{
super();
// Range uses index for seek instead of scan
this.query().dataSourceTable(tableNum(VendTable)).addRange(fieldNum(VendTable, VendGroup)).value('CONT');
}Result: Faster grid population, especially for 100k+ records.
Tip 3: Minimize Loops in Client-Side Methods Like run() or Control Events
Client-tier methods (e.g., run(), control modified()) are single-threaded and block the UI—heavy loops processing thousands of items cause freezes, high CPU usage, and unresponsive forms. Offload to server methods, use set-based operations, or chunk processing. Display methods in grids amplify this if looped naively.
Keep client code light; server-side loops don't block UI.
Example: Avoid client loops for calculations; move to server.
// Bad client loop - freezes UI
public void totalField_modified() // Client-tier
{
int i;
real total = 0;
for (i = 1; i <= 10000; i++)
{
total += someCalc(i);
}
this.Total = total;
}
// Better: Server static method
/**
* calcTotalOnServer
* ----------------
* Calculates total on server to avoid client UI blocking.
*
* September 22, 2025: Created by Jian Zhang for performance optimization article.
*/
server static real calcTotalOnServer(int _max)
{
int i;
real total = 0;
for (i = 1; i <= _max; i++)
{
total += someCalc(i);
}
return total;
}
// Call from client: this.Total = calcTotalOnServer(10000);This offloads computation, keeping the form responsive.
Tip 4: Defer Non-Essential Data Loading with Async Patterns
Synchronous loading in init() or run() blocks the UI until all data fetches, causing "white screen" delays on heavy forms. Defer secondary elements (e.g., FactBoxes, related transactions) using patterns like RunAs or SysTask—load essentials first, background the rest with callbacks to update UI.
X++ isn't truly async, but these simulate it without freezing. Essential for complex forms; otherwise, users wait unnecessarily.
Example: Defer secondary query in init() via RunAs.
/**
* init
* ----------------
* Initializes form, loading primary data sync and deferring secondary async.
*
* September 22, 2025: Created by Jian Zhang for performance optimization article.
*/
public void init()
{
next init();
// Primary sync
this.primaryDS().executeQuery();
// Defer secondary
runAs(this.hWnd(), classNum(MyForm_Extension), staticMethodStr(MyForm_Extension, loadSecondaryAsync), this);
}
/**
* loadSecondaryAsync
* ----------------
* Loads secondary data on server, callbacks to client for UI update.
*
* September 22, 2025: Created by Jian Zhang for performance optimization article.
*/
server static void loadSecondaryAsync(FormRun _formRun)
{
VendTrans vendTrans;
container results;
while select vendTrans where vendTrans.VendAccount == _formRun.vendTable().AccountNum
{
results += [vendTrans.TransDate, vendTrans.Amount];
}
_formRun.runOnClient(classNum(MyForm_Extension), staticMethodStr(MyForm_Extension, updateSecondaryUI), results);
}
/**
* updateSecondaryUI
* ----------------
* Updates UI with async results on client.
*
* September 22, 2025: Created by Jian Zhang for performance optimization article.
*/
client static void updateSecondaryUI(container _results)
{
FormListControl secondaryList = element.control(controlStr(FormName, SecondaryList));
int i;
for (i = 1; i <= conLen(_results); i += 2)
{
secondaryList.add(strFmt("%1: %2", conPeek(_results, i), conPeek(_results, i+1)));
}
}Form opens fast with main data; extras load without blocking.
Wrapping Up
These tips aren't theoretical—apply them bluntly to avoid common pitfalls like locked-up forms or scan-heavy queries. Profile with Trace Parser, test in multi-user setups, and remember: Extensions for everything to survive upgrades. If your forms still lag, it's likely deeper issues like bad joins—don't blame the tips.
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