bcquality/microsoft/knowledge/performance/batch-number-series-instead-of-getnextno-per-row.md

bc-version	domain	keywords	technologies	countries	application-area
22..	performance	no-series getnextno no-series-batch savestate numbersequence lock	al	w1	all

Batch number-series calls instead of GetNextNo per insert

Contributions welcome — open a PR to refine or extend this article.

Description

Codeunit "No. Series".GetNextNo on a gapless (Normal) series updates and locks the number-series line on every call. A tight Insert loop that asks for a number per row serializes every concurrent writer on that series — the classic SaaS posting bottleneck. Training data still copies the per-row C/AL NoSeriesManagement shape. Series configured with Allow Gaps instead obtain numbers through NumberSequence and do not hold the series-line lock between calls, so they are not affected by this pattern. Codeunit "No. Series - Batch" issues gapless numbers in memory and writes the series line once via SaveState.

Best Practice

Inside a multi-row insert, call "No. Series - Batch".GetNextNo per row and SaveState once after the loop when the series must remain gapless. Use NumberSequence.Next when holes are allowed. Do not replace a single OnInsert GetNextNo for one master record; that path is not the hotspot.

See sample: batch-number-series-instead-of-getnextno-per-row.good.al.

Anti Pattern

NoSeries.GetNextNo(...) inside repeat ... Insert ... until Next() = 0 where the series is gapless (Allow Gaps = false). Each iteration takes the series-line lock. The signal is "No. Series" (not "No. Series - Batch") in a loop that inserts more than one row; do not flag the same pattern when the series has Allow Gaps enabled, as the NumberSequence path already avoids the lock.

See sample: batch-number-series-instead-of-getnextno-per-row.bad.al.