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What's New in IDS 11.50 - January 2010 V2
On very logging active HDR primaries, checkpoint performance on the secondary can have a negative performance impact on the primary. If while the checkpoint is performed on the secondary, all HDR buffer resources fill, the secondary is then unable to receive more HDR buffers from the primary. At that point, there are also limited HDR buffers available on the primary, and when they fill, all logging activity on the primary halts until the checkpoint can complete on the secondary.

With log staging configured on the secondary, while the checkpoint is being performed, the HDR secondary will be able to continue to receive log data from the primary. This should prevent the primary from blocking logging activity because of no available HDR buffers.

To enable Log Staging you need to set 2 parameters in the ONCONFIG:
LOG_STAGING_DIR
LOG_INDEX_BUILDS
This feature was added in 11.50.xC6:
Documented in Administrator's Guide, Using High-Availability Data Replication chapter, section on “Prevent Blocking Checkpoints on HDR Servers”