Troubleshooting
Problem
This technote describes a scenario where it can come to performance degradation during Tivoli Storage Manager client backup because an unexpected high number of transactions is processed.
Resolving The Problem
In this scenario, the following settings have been defined:
Server->TxnGroupMax 256
Client-> TXNBYTELIMIT 25600
The following statistics have been reported by a client instrumentation trace:
Server Version 6, Release 3, Level 3.0
Data compression forced off by the server
Server date/time: 29-06-2006 12:00:05 Last access: 29-06-2006 09:15:07
Current command: Incremental
Total number of objects inspected: 74.819
Total number of objects backed up: 74.814
Total number of objects updated: 0
Total number of journal objects: 79.687
Total number of objects rebound: 0
Total number of objects deleted: 0
Total number of objects expired: 4.265
Total number of objects failed: 0
Total number of bytes transferred: 13,96 GB
LanFree data bytes: 0 B
Server-Free data bytes: 0 B
Data transfer time: 5.295,51 sec
Network data transfer rate: 2.766,04 KB/sec
Aggregate data transfer rate: 699,58 KB/sec
Total number of bytes pre-compress: 14.996.313.174
Total number of bytes post-compress: 14.996.313.174
Objects compressed by: 0%
Elapsed processing time: 05:48:57
Average file size: 195,74 KB
------------------------------------------------------------------
Detailed Instrumentation statistics for
Thread: 6328 Elapsed time 20937,580 sec
Section Actual (sec) Average(msec) Frequency used
---------------------------------------------------------
Process Dirs 0,000 0,0 0
Solve Tree 0,000 0,0 0
Compute 1,657 0,0 270984
BeginTxn Verb 0,141 0,0 11167
Transaction 48,856 4,4 11167
File I/O 299,004 1,0 307988
Compression 0,000 0,0 0
Encryption 0,000 0,0 0
CRC 0,000 0,0 0
Delta 0,000 0,0 0
Data Verb 2726,280 10,1 270984
Confirm Verb 0,000 0,0 1
EndTxn Verb 17755,910 1590,0 11167
Sleep 0,000 0,0 0
Thread Wait 85,075 2430,7 35
Other 20,657 0,0 0
------------------------------------------------------------------
Detailed Instrumentation statistics for
Thread: 6508 Elapsed time 20908,581 sec
Section Actual (sec) Average(msec) Frequency used
------------------------------------------------------------------
Process Dirs 0,000 0,0 0
Solve Tree 0,000 0,0 0
Compute 1,633 0,0 250649
BeginTxn Verb 0,076 0,0 11370
Transaction 49,845 4,4 11370
File I/O 304,188 1,1 288521
Compression 0,000 0,0 0
Encryption 0,000 0,0 0
CRC 0,000 0,0 0
Delta 0,000 0,0 0
Data Verb 2563,864 10,2 250649
Confirm Verb 0,110 110,0 1
EndTxn Verb 17901,403 1574,4 11370
Sleep 0,000 0,0 0
Thread Wait 72,014 1636,7 44
Other 15,448 0,0 0
------------------------------------------------------------------
From above client instrument:detail stats:
1) total # of files backed up: 74814
2) # of EndTxn's:
thread 6328: 11167
thread 6508: 11370
Total EndTxns: 22537 or avg # files/txn: 3.3.
With TXNBYTELIMIT=25600 KB , TxnGroupMax=256 and Average file size: 195,74 KB, it seems that the above stats show that Tivoli Storage Manager client is requesting way too many DB commits (EndTxn's) from Tivoli Storage Manager server.
Avg # of files/txn should be closer to 256, rather than 3.3 as calculated above.
Further investigation did show that different management classes with different copy destinations were configured for files and directories with this setup.
In this case, the directories on the fileservers changed just as much as the files, forcing Tivoli Storage Manager client to request EndTxn's every time it encountered files/dirs being backed up that are destined for a different MC during backup operation.
The change implemented in this case was to use the same management class for files and directories. The above example should give you a starting point to verify if you are facing this condition when running into performance problems during back up.
For more information on client instrumentation traces see 15.1.2 Tivoli Storage Manager client performance tracing in the IBM Tivoli Storage Manager Implementation Guide:
http://www.redbooks.ibm.com/redbooks/pdfs/sg245416.pdf
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Document Information
Modified date:
17 June 2018
UID
swg21247892