BC TechDays 2023 - Locking in AL: Runtime and explicit AL control

Recording of presentation at the BC TechDays 2023 conference of 22 & 23 June 2023 in Antwerp (Belgium)

Title: Locking in AL: Runtime and explicit AL control

Presenters: Mads Gram, Nikola Kukrika

Presented on Friday 23 June 2023, 13:30 - 15:00

Replaced video, as the previous recording was quite dark. Previous view counter was 502.

Contents (Thx to Marcus Nordlund):

00:23 Goals
03:06 Quiz
03:44 - Question 1. LockTable
04:48 - Question 2. Lock on a different variable
05:40 - Question 3. Read after write
06:13 - Question 4. Count after write
06:45 - Question 5. Findset
07:32 - Question 6: Conditional Insert
08:05 - Question 7: FlowFields
08:46 - Question 8: FlowFields
09:18 - Quiz Summary
10:02 Fundamentals
10:02 - AL´s interplay with the DB
11:54 - Transactions
12:34 -- Example: Post Sales Order
14:12 - Locks explained
16:55 -- SQL Server Lock compatibility matrix
18:58 -- SQL Lock escalation
20:01 -- Runtime determined locking
22:17 - Locks in VS Code debugger
23:09 - Advanced analysis SQL query (script to see current locks)
23:49 - Telemetry (find locker/victim via telemetry)
24:31 - Flowfields
25:11 Explicit control (ReadIsolation)
25:11 - Controlling reads explicitly
26:37 - ReadIsolation values - Used By default
28:17 - Question 2: Improved - Control example
29:19 - Pattern - Temporary heightening (Example: GetNextEntryNo)
32:09 - Pattern - Temporary lowering (Example: OnBerforeInsertEvent)
33:30 - ReadIsolationwith FlowFields
35:10 - Question 5: Avoid locking the entire table
36:30 - Pattern - Range Lock
36:50 - Think smart
39:23 Q&A
39:23 "Is it a good approach to always specify readisoloation for each read?"
41:35 "Are you going to switch to readcommitted?"
42:28 "Are all this on a session context? Not affecting other sessions"
42:28 "Possible to set standard ReadIsolation on NST?"

[marcusnordlund]

If you wonder what re-entrant is at 36:50 I looked it up for you ;)
"In computing, a computer program or subroutine is called reentrant if multiple invocations can safely run concurrently on multiple processors, or on a single-processor system, where a reentrant procedure can be interrupted in the middle of its execution and then safely be called again ("re-entered") before its previous invocations complete execution. The interruption could be caused by an internal action such as a jump or call, or by an external action such as an interrupt or signal, unlike recursion, where new invocations can only be caused by internal call."

[ДенисГапонов-иэ]

is abnywhere the example of the Isolation for Modify and Insert?