{"id":3565,"date":"2022-10-14T03:00:07","date_gmt":"2022-10-14T02:00:07","guid":{"rendered":"https:\/\/www.sebae.net\/blog\/deprecating-bad-item-limit-and-large-item-limit-migration-parameters\/"},"modified":"2022-10-14T03:00:07","modified_gmt":"2022-10-14T02:00:07","slug":"deprecating-bad-item-limit-and-large-item-limit-migration-parameters","status":"publish","type":"post","link":"https:\/\/www.sebae.net\/blog\/deprecating-bad-item-limit-and-large-item-limit-migration-parameters\/","title":{"rendered":"Deprecating bad item limit and large item limit migration parameters"},"content":{"rendered":"
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During a mailbox migration to Exchange Online, the migration process can expose some data inconsistencies in the form of bad (missing) items and\/or large items. A bad item is a corrupt item\/property in the source mailbox that cannot be copied to the target mailbox. A large item is an item in the source mailbox that is larger than the maximum message size in Exchange Online. Bad items and large items cannot be migrated to Exchange Online. Bad items and large items can also be encountered during onboarding public folders as well as off-boarding.<\/p>\n

Bad item limits (BIL) and large item limits (LIL) are used to set the maximum number of items allowed before a migration request fails. The BIL and LIL parameters are available in the Exchange admin center (EAC) and Exchange PowerShell cmdlets namely, Set-MoveRequest and New-MoveRequest. See this document<\/a> about message size limits that could impact migrations.<\/p>\n

Data Consistency Score (DCS)<\/a> can help alert the administrator when the data fidelity score during migration is less than optimal based on historical data for different contextual elements in a mailbox item (like property, permissions, calendar item, metadata, etc.) On the other hand, BIL requires admins to estimate<\/em> a BIL\/LIL limit at the start of the process without any data. BIL also doesn\u2019t have contextual or historical indicators for migration health and treats every type of corruption similarly. Thus, DCS not only helps eliminate corruption from user\u2019s mailbox, but also empowers users with data to identify items that can\u2019t be migrated. DCS empowers administrators to pass this information to the user being migrated to take action to preserve large items (as well as some corrupt items) in offline systems and prevents surprises after a migration is completed.<\/p>\n

DCS is being used as the default engine to track and report on data inconsistencies during migrations to Exchange Online. DCS considers the quantity of bad, missing, and large items encountered along with the understanding of message elements (e.g., message content vs metadata) in the current migration as well as historic migration data to compute and describe the data fidelity score of a migration. Links to documents describing DCS and scoring details are in the Resources section below.<\/p>\n

Currently, more than 90% of all onboarding migration jobs use DCS (instead of BIL\/LIL) and approximately 75% of these jobs get a perfect score. It is encouraging to see that users are benefiting from the improvements DCS provides. Thus, we have decided to fully deprecate BIL\/LIL and use DCS to measure and guide migration with data fidelity.<\/p>\n

What to expect?<\/span><\/h2>\n

With this change,<\/p>\n