How much Backed up: ActLog vs Summary

[Johnwkay72]

Trying to get accurate accounting of how much a node backs up. I have queried against both the ActLog and Summary tables. The weird thing is that when I do it I get 2 different numbers. The Actlog and the Summary tables appear to be different. Might be +/- 3%

Example: (server names have been changed to protect the innocent)
-- Servers are using a 24 hour cycle (1 time per day) --
-- Select statement filter from summary table for ONLY "BACKUP' activities --
-- Time stamp from ActLog and Summary tables match --

Svr-A: ActLog = 445.89 MB // Summary table = 467376531 bytes.
Convert to Bytes to normalize = 467549552.64 // 467376531
Difference = -173021.64 or -0.04%

This might not seem significant but when you are backing up 10+ TB of incremental data a day that Variance adds up. This effects the TIP/TEP and their data warehouse too.

Does anyone out there have an idea why there is a difference?

 

[moon-buddy]

Here is what I understand how things are handled:

The Actlog keeps a record of what transpired. The Summary table takes what is actually recorded. This means that the Summary table contains the actual recorded information.

As for the difference, it has what TSM sees during transfers (Actlog) which may not be what actually was written (Summary).

But, I may be wrong in my understanding how TSM handles data transfers.

 

[Johnwkay72]

Moon-Buddy
That sounds reasonable. There is meta-data which has to be transmitted during a backup operation. The ActLog does say "transmitted" which is probably not the same definition of "backed up".

The devil is always in the details.
Thanks

 

[marclant]

The actlog shows the client stats as seen in the dsmsched.log. The bytes transferred only includes data.

The summary table is the bytes transmitted for the session, including db queries and updates.