bcquality/custom/knowledge/performance/pure-reads-set-readisolation.md

bc-version	domain	keywords	technologies	countries	application-area
all	performance	readisolation readuncommitted pure-read get findset findfirst findlast	al	w1	all

Set ReadIsolation explicitly on pure reads

Description

In TCOG apps, pure reads should set an explicit ReadIsolation on the record instance before the read operation. This makes the read semantics intentional instead of inheriting whatever isolation level happens to be active in the surrounding transaction or caller. For display, lookup, and calculation helpers that only read data and do not make decisions that require committed consistency, the default convention is IsolationLevel::ReadUncommitted.

Best Practice

Before a pure read such as Get, FindSet, FindFirst, FindLast, or a read-only existence or aggregation call, set Rec.ReadIsolation(IsolationLevel::ReadUncommitted); on the specific record instance, then perform the read. Use a stronger isolation level only when the procedure's functional contract requires committed or repeatable data.

Anti Pattern

A read-only helper performs Get, FindSet, or another pure read without setting ReadIsolation on the record variable first. The code works, but the locking and consistency behavior is left implicit and can drift with surrounding transaction context. On hot paths such as page calculations, lookups, and repeated helper calls, this creates inconsistent conventions and makes concurrency behavior harder to reason about.