Exchange Server Subscription Edition: Dynamic Circular Logging not Truncating for Exchange Database

Harris, Ricardo 0 Reputation points
2026-10-06T15:14:37.8466667+00:00

Hello,

I am hoping that someone can provide some insight and direction.

My organization is configured with multiple DAGs.

One of the sites that have Exchange Servers associated with the DAGs and having DB copies needed to be powered down for a period of time.

Due to specific Databases being hundreds of Gigabytes and sites not being in the same geographic location, the decision was made to have Circular Logging enabled on DBs with copies while the specific Exchange Servers with Database copies are powered off. This way DB seeding operations for multiple databases to the specific servers would not have to be done.

It was known prior to shutting down the specific servers that DB logs would not be truncated following a DB log backups.

Circular Logging was enabled on DBs having copies prior to shutting down the specific servers that needed to be powered off. It was also confirmed that logs were truncated after enabling Circular Logging.

Two days later it was discovered that DB logs were accumulating and not being truncated by Circular Logging.

Are there options for logs to be truncated while the specific Exchange Servers are offiline and having circular logging enabled?

Or, must the DB copies associated with the specific Exchange Servers that are offiline need to be removed to allow logs to truncate for DB copies that are online.

Since the discovery of log accumulation, DB log disk drives have been given more space to prevent logs from running out of space. This is not the desired solution while the specific Exchange Servers are offiline. A more optimal solution is needed.

Exchange | Exchange Server | Management
Exchange | Exchange Server | Management

The administration and maintenance of Microsoft Exchange Server to ensure secure, reliable, and efficient email and collaboration services across an organization.

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  1. Kai-L 19,920 Reputation points Microsoft External Staff Moderator
    2026-10-06T15:56:23.31+00:00

    Dear Ricardo,

    Thank you for the detailed explanation. Unfortunately, as a forum moderator, I am not able to review your DAG or change its configuration directly. My role here is limited to providing general guidance you can apply from your side.

    From my research, what you're seeing is expected with continuous replication circular logging (CRCL). On a non-lagged copy, a log can only be truncated when the other non-lagged copies of that database agree to the deletion. The copies on the powered-off servers are still configured, so Exchange keeps the logs they would need to catch up, and those copies can't confirm the deletion while they're offline. That explains why truncation worked right after you enabled circular logging and stopped once the servers went down.

    As far as I know, there's no CRCL setting that truncates those logs while still keeping the offline copies able to catch up. That leaves two practical options:

    1. Bring the servers online periodically so the copies catch up and CRCL can truncate the logs.
    2. Remove the offline database copies for the duration of the outage, so the online copies can agree on truncation. Then add the copies back and reseed them when the site returns.

    If the outage will be long and adding disk space isn't sustainable, option 2 is usually the cleaner choice, although it means reseeding later. When you re-add the copies, keep in mind that if a database is back to only one other copy, you'll need to disable circular logging before adding its second copy. Third and later copies can be added with CRCL still enabled.

    That said, if neither option suits your situation, I'd recommend opening a service request with Microsoft Support through your organization's support agreement. An Exchange support engineer can review your DAG configuration and the expected length of the outage, and may be able to suggest a better approach for your environment. For detailed instructions on how to get support, please refer to Get support - Microsoft 365 admin.

    I hope this helps. Looking forward to your reply.

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