It’s a good question . There are few situations like . where storage is filling up faster because of log files . where databases having more database copies . and there is no enough storage available to withstand the situation.
So we will be forced to enable Circular logging in these situation, still its not recommended to do so .
What is Circular logging ? – for starters
To prevent a buildup of log files, you enable circular logging for your replicated databases. When you combine circular logging with continuous replication, you have a new type of circular logging called continuous replication circular logging (CRCL), which is different from Extensible Storage Engine (ESE) circular logging. Whereas ESE circular logging is performed and managed by the Microsoft Exchange Information Store service, CRCL is performed and managed by the Microsoft Exchange Replication service. When enabled, ESE circular logging doesn’t generate additional log files and instead overwrites the current log file when needed. However, in a continuous replication environment, log files are needed for log shipping and replay. As a result, when you enable CRCL, the current log file isn’t overwritten and closed log files are generated for the log shipping and replay process.
So the question is , is it safe ? to Enable circular logging in Exchange Databases which are mounted ?
Yes, And not all the databases in one shot – – It may get your replication network down (Totally depends on the your situation, Read through )
If I enable circular logging in Exchange 2013. is my logs are going purge itself ?
Yes , It will be purged automatically by information store service.
Is all my database copies logs will be purged ?
Yes , it re synchronizes the logs and it will be purged in all database copies , it may few hours depends on the database size.
Example : Like 200 GB of database with 300 GB logs takes 3 to 4 hours in Blade servers
is it safe to enable Circular logging in business hours ?
No, Its totally depends on the size of the logs file you have with your databases , If there are more GB’s of log files .(they are going to resynchronize) which will increase more bandwidth on the replication network.
Still if the databases is too busy in Read/write data. it will put more load on storage in the process of removing those old log files
Will I Need to restart information store service ?
No , It should react in few minutes and resynchronize the logs in few hours . (In my case it didn’t require a restart, I cannot assure in all the environments)
How to Enable Circular logging in a database ?
To Enable :
Set-MailboxDatabase “DatabaseName” -CircularLoggingEnabled:$True
Set-MailboxDatabase “DatabaseName” -CircularLoggingEnabled:$False
To Enable Circular logging in all databases
Get-mailboxdatabase | Set-MailboxDatabase -CircularLoggingEnabled:$True
To Disable Circular logging in all databases
Get-mailboxdatabase | Set-MailboxDatabase -CircularLoggingEnabled:$False
Hope this article was informative