Oracle Backup slowness - Networker

You need to first be ruling out NW altogether, what are results of for example dd testing trying to read and write data to and from the filesystems that contain the Oracle DB data to be backed up? As filesystem backup seems to suggest it is also slower for those filesystems, compared to other filesystems?

So any testing is first to be performed from the client to and from its own storage and then work from there. If dd or similar tests (can't recall what kinda performance tests can be run on a AIX system) show performance is slow, then backup will encounter the same thing. So any testing would be performed, and possibly the result might show not having to do anything with Networker or any backup product...

Most likely if you have good reads from /a and slower reads from /b given that it is same host - difference is storage path (assuming it is not fs related and it is unlikely to be).   You can create some random data file of couple GB size and place it on /a and /b (whatever would be corrensponding good and bad performance fs in your case).  Then use some tool to read data into memory (in your case reads are related to backup performance) and see if there is difference.  Your AIX admin will probably come up with some imaginative test scenarios in combination with iostat.

try increasing channel