AIR image imports on target NBU lag behind
We have 2 NetBackup master servers (8.0 on Solaris 11, ddboost version 3.3) and 2 data domains (DDOS 6.1.x) in 2 data centers. They are using SLP and AIR to replicate backup images. The backups and replications from source NBU are running fine. The images can be replicated fairly fast to the destination data domain. However, SLP imports on the destination NBU are lagging behind since last month. As of today, the target NBU is importing the replicated images from 5 days ago, and there are still around 5000 items in the target server's event folder. I have tweaked the SLP parameters on the target NBU, but it didn't help too much.
We have disabled replication and wait for the SLP import on target NBU to catch up. But the SLP imports are still going slowly. At this pace, the import queue on target NBU can be cleared in 2 days. My concern is once we enable the replication, the images hold up from source NBU will flood the target's queue again. The target NBU will never be able to catch up the latest replications.
I run "nbstlutil stlilist -image_incomplete -U" on the target NBU from time to time to check the import progress. The imports are running, just not as fast as I hope.
My options are trying to find a way to speed up the SLP import or manually clean up the import queue. I like to hear from any experts to find out if anyone else faced this kind of problem before and any possible solutions.