Importing hundreds of thousands of records is well within the tool’s capability, and timing scales roughly in proportion to the number of records and the settings you use. This is a completely free app from Insight Works for Business Central. As a rough guide, a load of one hundred thousand records may take on the order of several minutes to around twenty minutes depending on the table and the options enabled, which is dramatically faster than RapidStart, which often will not finish a load of that size at all.
How import time scales
Import time is close to linear, which means that if a smaller load of a given table takes a certain amount of time, a load ten times larger will take roughly ten times as long. This predictability makes it easy to estimate a large job from a small test. For perspective, a load of a few thousand records typically completes in well under a minute, so multiplying up gives you a reasonable expectation for a much larger file. Files in the tens of megabytes with hundreds of thousands of rows import successfully; the practical consideration is total elapsed time, not whether the Import Export PowerTool can handle the volume.
What slows an import down
Several factors increase import time. Validating fields runs the underlying Microsoft Dynamics 365 Business Central business logic for each validated field, which adds work, so validate only the fields that truly need it. Importing dimensions alongside records adds processing and noticeably increases the time. Running the on insert or on modify business logic also adds overhead, as does the two step insert option, which performs an insert followed by an update. Each of these is sometimes necessary for correctness, so the goal is to enable only what a given load requires.
What speeds an import up
To make a large import as fast as possible, validate the minimum set of fields, for example the key account or item field that drives defaults, and leave purely informational fields unvalidated. Disable the on insert and on modify logic when you are confident the data is complete and does not need that processing. Temporarily disabling the change log can substantially reduce time on bulk loads, since it avoids generating a change log entry for every record, though this removes that part of the audit trail, so use it deliberately. Note also that the first run of an operation is slower while Business Central caches the relevant code and data; subsequent runs of the same operation are quicker.
Planning a very large load
For a job in the hundreds of thousands, run a representative sample first, measure the time, and scale up to estimate the full duration. Decide on your validation and logic settings based on that test, and schedule the full load for a window where the elapsed time is acceptable. Because the tool writes directly and rolls back by table on error, validating your file in advance avoids a long run that fails late and has to be repeated.
Related Tools
Import Export PowerTool is the Insight Works app for fast import, export, update, and delete operations in Business Central. Its validation, business logic, and change log options are the main levers for tuning the speed of very large imports.
Hundreds of thousands of records are entirely feasible. Expect timing to scale with volume, test with a sample to estimate the full run, and tune the validation, business logic, and change log settings to balance speed against the correctness and audit trail you need.