We are running exchange server 2013 with CU6, on windows serVER 2012.
very frequently, content index is getting failed. Not sure why this issue has become more but we have been affected by this issue more than any oher issue.
Seems like it fixes automatically after sometime, but during production hours most of the databases content idex is failed.

I ran the below command but that didn't fixed the issue:

Update-mailboxdatabasecopy -identity "Database name" -catalogonly -deleteexistingfiles

Error message that i got when i ran the command:

WARNING: Seeding of content index catalog for database failed. Please verify that the Microsoft
Search (Exchange) and the Host Controller service for Exchange services are running and try the operation again. Error:
 The seeding operation failed. Error: An error occurred while performing the seed operation. Error: An error occurred
while updating the search catalog files from server 'ECSJNC00102-N3.sjab.local' to 'server name'. Error:
A transient exception from Exchange Search was encountered. Error: -1..

Not sure what is the issue, whether it is a bug or known issue, but need to fix.

please share your thoughts.

This could be your solution.  I have seen it happen at a couple of my clients:

https://support.microsoft.com/en-us/kb/2807668

Hi,

For your question, please run Get-MailboxDatabaseCopyStatus -Server servername | FL Name,Status,ContentIndex* to Check the database copy indexing health. More information to troubleshooting Exchange search issue, please refer to:
https://technet.microsoft.com/en-us/library/bb123701(v=exchg.150).aspx

If the issue persists, please try to  suspend the database copy, delete the catalogdata folder on the target mailbox server and then try to use Update-MailboxDatabaseCopy with -Catalogonly to rebuild the catalog.

Thanks