none
DPM 2019 | EXCHANGE SERVER 2016 | LOG TRUNCATION RRS feed

  • Question

  • Hi DPM Team,

    I installed DPM 2019 because it is Microsoft Product and it will be best to backup Microsoft products. I was shocked to see it doesn't truncate logs after Exchange 2016 Database Backups. Here it is increasing 'Administrative efforts".

    1.) There must be some strong reason behind "not flushing logs", please share it with me so that as an Admin I can justify my product selection.

    2.) For some reason, Log Truncation is not happening, please suggest best script or some way to truncate logs safely. I've seen one article with three methods, a) dismount and mount, b) initiate vss backup and end, c) manually delete the logs.

    3. Like most other backup software, is there a way to select type of backup, "full, incremental, differential" etc

    Please suggest best way to truncate logs.

    Thanks


    Fahad

    Wednesday, June 24, 2020 4:49 AM

All replies

  • Hi Fahad,

    To be able to truncate the exchange Logs after successful backup we need to make sure protection group has the following settings.

    First configure one full backup per day, and a synchronization frequency to suit your requirements for Exchange log truncations. When protecting more than one copy of an Exchange mailbox database (for example, when protecting members of a DAG), configure one node for full backups and the rest for copy backups. Copy backups do not truncate log files.

    DPM does not support differential backups, it supports Incremental backup and Full backups only. Sync Frequency represents the incremental backup and Full/Expressfull backup represents the Full backup along with "SYNC Just before recovery point."

    If all these settings are in place, you dont need to truncate logs manually. Please share your protection group settings and schedule you are using? 

    Wednesday, June 24, 2020 5:31 AM
  • Hi Fahad,

    You need to configure one full backup per day, and a synchronization frequency to suit your requirements for Exchange log truncations.

    When protecting more than one copy of an Exchange mailbox database (for example, when protecting members of a DAG), configure one node for full backups and the rest for copy backups. Copy backups do not truncate log files.

    Also are your Exchange servers virtualized on Hyper-V?

    Best regards,
    Leon


    Blog: https://thesystemcenterblog.com LinkedIn:


    • Edited by Leon Laude Wednesday, June 24, 2020 8:40 AM
    Wednesday, June 24, 2020 8:31 AM
  • Hi Everyone,

    we have 2 physical servers with DAG and for testing purpose I created a new DB and a single mailbox on it.

    Server A & Server B, DB1 is mounted on Server A, Passive copy on Server B

    B). Day 2, I configured full backup for Server B and Copy backup for Server A ( I thought this made sense because the logs would flush after committing to second passive copy,

    sync: 8 Hours,
    express full backup: 10 AM

    next day I noticed the status on the database had changed and it showed the status of full & incr backup. There we still 300 logs like yesterday.

    C). Day 3, I configured full backup for Server B (I don't want backup of 2 copies, as it saves space and it is faster.

    sync: 6 Hours,
    express full backup: 1 PM

    next day I noticed the status on the database had changed and it showed the status of full & incr backup. There we still 250 logs.

    In the protection group, should we select the Database name or expand it and select server name we want to backup. Also, what is the reason behind backing 2 copies, if we have backup of one good copy it is enough to restore a DB or a single mailbox right.

    https://social.technet.microsoft.com/Forums/en-US/3c96baba-6fe2-4ed9-80fe-e9a97c6a0123/dpm-doesnt-clear-transaction-logs?forum=dpmexchbackup

    While reading about truncating logs, i came across this article and wondered why is it so? Also, I called up my friend in another company who handles DPM Backup and I inquired with him, He says, his exchange admin has written a script to manually clear the logs.

    My understanding about clearing the logs is, after the backup job is completed, it should have nearly less than 10 logs left in that folder.


    Fahad

    Thursday, June 25, 2020 4:14 AM
  • Your DPM backup settings is okay and so DPM is doing it part however we need to check few more things from exchange side. As far as I remember there is a certain threshold for exchange before it start truncating the logs. As you mentioned you had 300 logs yesterday and the next day it is  sitting at 250 logs. So it looks like 50 logs has been truncated which was under the given threshold.

    First, log truncation will only trigger is VSS Full backup is completed for a given database, to figure out this you can run below PS cmdlets on the exchange server and it will give the timestamp


    Get-MailboxDatabase -Status | ft Name,*FullBackup

    If DB full backup time is visible, then you need to check below conditions from Exchange perspective. Please note that DPM is not responsible for Log truncation for Exchange or SQL. It needs to be investigate from application side. 

    ---------------------------------------------------------------------------------------------------------------

    The following criteria must be met for a database copy's log file to be truncated when lag settings are left at their default values of 0 (disabled):

    The log file must have been successfully backed up, or circular logging must be enabled.

    The log file must be below the checkpoint (the minimum log file required for recovery) for the database.

    All other lagged copies must have inspected the log file.

    All other copies (not lagged copies) must have replayed the log file.

    The following criteria must be met for truncation to occur for a lagged database copy:

    The log file must be below the checkpoint for the database.

    The log file must be older than ReplayLagTime + TruncationLagTime.

    The log file must have been truncated on the active copy.

    Source: https://docs.microsoft.com/en-us/exchange/managing-mailbox-database-copies-exchange-2013-help?redirectedfrom=MSDN


    Thursday, June 25, 2020 6:06 AM
  • If DPM is not responsible for log truncation then am I responsible?

    Ha ha Jokes apart, please confirm if your product flushes logs or just truncates a few randomly or it does nothing.

    I created a new database and a new single mailbox on it. I sent a couple of emails to increase logs and monitored the logs. Before going on weekend (thu) I dismounted and mounted the database to check how many logs are there. The number reduced to 198.

    After weekend on Sunday I checked the logs were nearly 300. As per earlier link I shared I can understand if there 100-150 logs after full backup of DB. I cannot understand why there are 300 logs and three days old logs.

    Did anyone of you really tried in a lab environment? Please share the screenshots of before and after the full job completes and also all job settings.

    I cannot share screenshots because of security reasons but I would really appreciate if there is someone out there with screenshots.

    If someone has good links to learn and understand dpm deeply please share.

    Even if there is a good e-learning course please refer.

    Can I initiate an adhoc full backup at my leisure?If so please share how?

    Does DPM PowerShell has extra commands and switches not available in GUI?

    Thanks in advance


    Fahad


    • Edited by Fahad1981 Wednesday, July 1, 2020 5:17 AM
    Tuesday, June 30, 2020 9:07 PM
  • Below are the answers to your questions:

    If DPM is not responsible for log truncation then am I responsible?

    Extensible Storage Engine is responsible for long truncation. To be more specific: The JetOSSnapshotTruncateLogInstance function truncates the log for a specified instance during a snapshot session. These are exchange components only. JetOSSnapshotTruncateLogInstance is a Subset of Extensible Storage Engine function. Read here for more information.

    Ha ha Jokes apart, please confirm if your product flushes logs or just truncates a few randomly or it does nothing

    DPM is designed to take backups only. It is not designed to do anything else. DPM does not flushes or truncates exchange log backups.

    If someone has good links to learn and understand dpm deeply please share.

    Going though the DPM forum discussion will help you a lot. You can also browse through the Docs pages to learn more about DPM. However this will still not answer the truncation logic as it is only handled at exchange side.

    Can I initiate an adhoc full backup at my leisure?If so please share how?

    Yes- On the DPM console, under protection tab, select your Protection group under which exchange Dbs are protected, right click on the DB and select - Create Recovery point By using ExpressFull backup. It will trigger the full backup for your DBs provided that it is selected for Full backup for DAG configuration.

    Does DPM PowerShell has extra commands and switches not available in GUI?

    Not really. You should be good using UI and it will suffice your need. 

    Did you run the powershell commands I mentioned in my last post? Did it show the last full backup time stamp for your Database? This time stamp is only from DPM prospected. If it is showing the time stamp, DPM is working absolutely fine. 

    I am sharing some other forum discussion regarding Exchange log truncation topic. It might help you understand the truncation process a bit more. Do let me know if you have follow up queries.

    https://social.technet.microsoft.com/Forums/ie/en-US/a6b2ccb3-7549-4e8e-beb8-bdaa7f376e53/log-files-not-truncating-with-windows-server-backup?forum=exchangesvradmin

    https://social.technet.microsoft.com/Forums/office/en-US/90aa9b29-d87d-4d06-ad88-5783f6a64035/exchange-2019-transaction-log-truncation-issue?forum=Exch2019


    Wednesday, July 1, 2020 6:44 AM