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bcquality/microsoft/knowledge/performance/al-methods-limited-during-write-transactions.md
Michael Dieringer fb896e9734 Correct XmlPort.RunModal to Xmlport.Run; fix READ-convention sample links 
XmlPort has no RunModal method (static or instance) - Microsoft Learn
confirms only Xmlport.Run(Integer [, Boolean RequestWindow] [, Boolean]
[, var Record]). Replaces the invented API with the real one throughout
the article, worklist cue, and token list, and explains the platform
error message's own "XmlPort.RunModal" wording as the same kind of
legacy phrasing already noted for Form.RunModal/RequestForm.

Also corrects UseRequestPage(false): that's a Report instance method
only, not applicable to XMLport, which uses the UseRequestPage = false
object property or Run's RequestWindow argument instead.

Fixes the two sample references to use the READ-convention markdown
link form (Test-KnowledgeIndex.ps1's Knowledge-Retrieval.ps1 check was
failing on plain backtick text).

Rebased onto upstream/main to resolve conflicts with #148's job-queue
additions to al-performance-review.md - both sets of worklist tokens
and cues are retained.
2026-09-21 22:01:07 +02:00

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bc-version domain keywords technologies countries application-area
all
performance
limited-during-write-transactions
write-transaction
runmodal
form-runmodal
page-runmodal
report-runmodal
xmlport-run
codeunit-run
commit
requestpage
al
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all

AL methods limited during write transactions: commit before RunModal and Codeunit.Run

Description

Once AL code has written to the database in the current transaction — an Insert, Modify, or Delete with no Commit since — the platform restricts four methods until that transaction is committed. The exact conditions, as enforced:

  • Page.RunModal — not allowed in a write transaction, under any circumstances.
  • Report.RunModal — allowed only if the request page is suppressed: Report.RunModal(ReportId, false) (the second argument is RequestWindow), or UseRequestPage(false) on a report instance. With a request page it fails.
  • Xmlport.Run — same rule when it would show a request page: allowed only if the request page is suppressed, Xmlport.Run(XmlPortId, false) (the second argument is RequestWindow) or the UseRequestPage = false; object property. With a request page shown it fails. There is no XmlPort.RunModal method — see the note on the platform's error text below.
  • Codeunit.Run — allowed only if its Boolean return value is not used. OK := Codeunit.Run() and if Codeunit.Run() then fail, because that form commits — see codeunit-run-requires-prior-commit-inside-transaction.md.

This is a runtime error, not a compiler diagnostic: the code builds, and the first execution that reaches the call with an open write transaction dies. The guard keys on transaction state alone, not on any relation between what was written and what is opened: an Item.Insert() followed by Page.RunModal(Page::"Customer Card") — an unrelated table — fails on the RunModal line, and because the error stops the transaction, the insert rolls back with it.

The platform's message (Business Central 26, reproduced 2026-09-07) reads: "The following AL methods are limited during write transactions because one or more tables will be locked: Form.RunModal, Codeunit.Run, Report.RunModal, XmlPort.RunModal. Form.RunModal is not allowed in write transactions. Codeunit.Run is allowed in write transactions only if the return value is not used. For example, 'OK := Codeunit.Run()' is not allowed. Report.RunModal is allowed in write transactions only if 'RequestForm = false'. For example, 'Report.RunModal(...,false)' is allowed. XmlPort.RunModal is allowed in write transactions only if 'RequestForm = false'. For example, 'XmlPort.RunModal(...,false)' is allowed. Use the commit method to save the changes before this call, or structure the code differently." The message still uses the legacy names Form.RunModal and RequestForm even though the AL method is Page.RunModal and the report parameter is RequestWindow; older versions said "C/AL functions" instead of "AL methods" (microsoft/AL#5452, 2019). The message also names XmlPort.RunModal, which is legacy phrasing too — there is no such AL method; the actual API the guard applies to is Xmlport.Run, and the message's RequestForm = false condition corresponds to Xmlport.Run's RequestWindow argument or the UseRequestPage property. The behavior is unchanged across versions.

The reason is the same one behind avoid-user-prompts-inside-transactions.md: a modal object waits for the user, and the platform will not let a write transaction — and every lock it holds — sit open for as long as that takes. The difference is enforcement. Confirm and StrMenu are allowed inside a write transaction and silently hold the locks; RunModal is refused. Both point at the same design fix.

Best Practice

Sequence the work so the modal interaction happens before the write phase: run the lookup or dialog page first, then perform the writes the user's choice requires, and let the transaction end. When a modal object genuinely must follow a write, Commit() first — but only when the state written so far is complete and safe to persist on its own, because that Commit is a real transaction boundary, not a formality. Microsoft's own Base Application follows exactly this pattern where the preceding state is final (ActivityLog.Table.al commits the log entry before Page.RunModal(Page::"Activity Log", Rec); DocumentSendingProfile.Table.al commits before Page.RunModal(Page::"Select Sending Options", …)). For a report, suppressing the request page — Report.UseRequestPage(false) on a report instance, or false as the RequestWindow argument to Run/RunModal — is a legitimate way to run it inside a write transaction when no user input is needed. For an XMLport, the equivalent is false as the RequestWindow argument to Xmlport.Run, or the UseRequestPage = false; object property; XMLports have no instance UseRequestPage method. Database.IsInWriteTransaction() (runtime 11.0+) lets library code that cannot control its caller detect the state, with the same caveat as the Codeunit.Run article: branching production flow on it usually signals unclear transaction ownership.

See sample: al-methods-limited-during-write-transactions.good.al.

Anti Pattern

Writing to the database and then calling Page.RunModal (or a report/XMLport with its request page) in the same trigger — the first production run hits the runtime error. The reflexive fixes are worse than the error: dropping in Commit() to silence it persists a half-finished state that can no longer roll back with the rest of the operation, and swapping the page for a Confirm or StrMenu to "avoid the error" trades a loud failure for the silent lock-holding that avoid-user-prompts-inside-transactions.md warns about.

See sample: al-methods-limited-during-write-transactions.bad.al.

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