Slow DB2 DB Backups / Fast Log Backups
i've a question regarding DB2 Backups.
We have DB2 on AIX and the problem are slow DB2 database Backups, the Log Backups on the other hand are running very well.
DB Backups are done to SAN connected LTO5 drives and I get 50-70 MB/s. This is way to slow for the storage and the tape drives.
Log backups are network backups to a media server with DSSU connected. The logs are to small to give reliable speed counters.
I found a huge difference between the two backups regarding buffers, but first these are the buffers setting on the client:
I have never tweaked NET_SZ_BUFFER or any other buffer setting. The BACKUP DB command from the script NetBackup starts for DB2 Backups is not tweaked either, except the OPEN 8 SESSION and INCLUDE LOGS statement.
But I see a weired behavior in the backups itself.
This is from a DB Backup:
Info bpbkar(pid=59572348) dbclient(pid=59572348) wrote first buffer(size=4096)
This is form a log backup
Info bphdb(pid=65536066) dbclient(pid=65536066) wrote first buffer(size=131072)
Why is the DB backups using bpkar and a 4096k buffer and the log backup is unsing bphdb and 131072k buffer?
This would explain the slow data transfer to the tape drives.
Can someone explain this a litte further? And how can I increase this bpkar/dbclient buffer.