The Challenge
Refresh operations are a critical part of iCluster replication. They move full object copies from source to target, and for large environments the time and bandwidth they consume directly impacts replication windows and recovery readiness.
Until now, iCluster offered four compression options for SAVRST refresh processing — *NO, *YES, *MEDIUM, and *HIGH — all based on the traditional IBM i compression algorithms. While effective, these options left performance on the table, especially on modern Power hardware.
What Changed
iCluster now supports *ZLIB compression to accelerate refresh operations and improve replication efficiency for IBM i environments.
The new *ZLIB option is added directly to the existing Object Compression setting in iCluster System Values (DMSETSVAL), which previously supported *NO, *YES, *MEDIUM, and *HIGH. This makes adoption straightforward — customers can enable *ZLIB compression using the same familiar system-value configuration they already know.
One setting in DMSETSVAL. Up to 5x faster refresh. No new workflow to learn.
Why It Matters
- Up to 5x Faster Refresh — Objects refreshed in SAVRST format can complete dramatically faster with *ZLIB enabled.
- Lower Network Usage — Strong compression efficiency reduces data transferred across the network during refresh operations.
- Zero Workflow Change — Uses the existing DMSETSVAL setting. No new commands, no new configuration steps.
When running on systems that support hardware acceleration — specifically the Power10 NX GZIP feature — *ZLIB compression can significantly reduce refresh times while maintaining excellent compression efficiency. This helps customers shorten replication windows, reduce network usage, and better utilize modern IBM Power platforms.
How to Enable It
Enabling *ZLIB compression takes a single change:
- Open iCluster System Values (DMSETSVAL).
- Navigate to the Object Compression setting.
- Select *ZLIB from the available options.
That's it. Refresh operations will begin using ZLIB compression on the next refresh cycle. No restart required, no additional configuration.
Platform Requirements
- iCluster version: 9.4.1 or later
- IBM i version: IBM i 7.5, or IBM i 7.4 TR7 with required PTFs
- Hardware acceleration: Power10 with on-chip NX GZIP (optional, for best performance)
- Refresh format: SAVRST (Save/Restore)
Compression Options at a Glance
- *NO — No compression applied during refresh
- *YES — Standard IBM i compression
- *MEDIUM — Balanced compression with moderate CPU usage
- *HIGH — Maximum compression ratio, higher CPU cost
- *ZLIB (NEW) — ZLIB-based compression; up to 5x faster on SAVRST refresh with Power10 NX GZIP acceleration
Ready to Speed Up Your Refresh?
Upgrade to iCluster 9.4.1, set *ZLIB in DMSETSVAL, and let your next refresh speak for itself.
