What to check before changing storage settings
A catalog stores organisation and editing information; originals supply the photograph's source pixels. Preview caches help browsing, while Smart Previews and full offline copies support different kinds of disconnected work. These files are not interchangeable. Start with File → Catalog Maintenance → Overview… to see the actual locations and usage for the current catalog.
Read an integrity result
Choose Check Catalog Integrity… and wait for the background check. The maintenance window keeps the result visible. Show report gives the check time, locations and individual outcomes; Copy report lets you retain or share the diagnostic text.
A successful check means the checked catalog/Develop databases and references passed their structural checks. It does not prove every original is readable, every edit looks right or every backup is restorable. The check makes no repairs. If it reports an error, retain the current catalog and recover a verified backup into a separate folder before judging the result.
Back up the right things
Back up now reports success or failure and the saved destination. Full catalog backups include catalog and Develop data, imported masks and editable repair data. Keep separate backups of original photo folders and external profiles/LUTs. Full offline working copies are not included in the catalog backup bundle.
A useful check is to restore a backup as a separate recovered catalog, open several edited photographs and confirm that their sources and dependent assets are available. Do not overwrite the only current catalog while investigating damage.
Disk cache and memory controls
| Control or storage | What it does | When to change it |
|---|---|---|
| Maximum cache size | Limits disposable browsing previews; default 4 GiB | Increase if you revisit large collections and have disk space |
| Current usage / free space | Shows actual use and remaining storage | Check before a large import or making offline copies |
| Clear preview cache | Removes disposable preview sizes | Use to reclaim space or investigate a bad cached preview; it is not a routine speed-up |
| Automatic memory allocation | Budgets a quarter of detected RAM, up to 8 GiB | A suitable starting point for most systems |
| Custom Memory budget | Sets a reusable-image/processing budget | Leave room for other applications and AI workers; this is not a hard process-memory cap |
| Faster fitted previews | Uses a smaller live preview during interaction | Leave enabled for responsive adjustment; detail returns on release |
| Process exports at full resolution | Processes at source size and downsizes last | Use when the full-resolution processing tradeoff matters; it costs more time |
Previews are reused on disk between sessions, and recent photo records are kept in memory. The cache limit is filled as previews are generated; the app does not reserve that whole amount in advance. Older browsing previews are cleaned automatically, so a busy import may briefly exceed the target.
Clearing the preview cache preserves originals, catalog data, editing history, edited preview masters, Smart Previews and full offline copies. Browsing previews then have to be regenerated, so an immediate revisit can be slower.
Preview, offline copy or backup?
| File type | Offline editing | Full-quality export | Replaces a photo backup? |
|---|---|---|---|
| Browsing thumbnail / preview cache | Not a complete editing source | No | No |
| Smart Preview | Yes, at reduced source resolution | No; reconnect the original/full copy | No |
| Verified full offline copy | Yes, with all source pixels | Yes | No; it is a working copy |
| Original photograph | Yes, when accessible | Yes | Keep an independent backup |
| Catalog backup | Restores organisation and edits | Needs source photos as well | Does not include originals |
The complete offline workflows below explain how to build, verify, remove and move these persistent sources. Keep the catalog on reliable accessible storage, wait for background jobs to finish before disconnecting a drive, and judge full-detail tools using the full source.
Offline originals
Select photos in Library, then choose File → Offline Originals → Keep Selection Available Offline. OmaRAW makes verified, full-quality working copies on the machine. A RAW copy takes as much space as its original. Variants share one copy of their source file.
Wait for the job to finish before disconnecting the original drive. Progress appears in the status line; Cancel Offline Copy Job stops remaining work and retains completed copies. The Library inspector shows the saved copy's size and whether the original is disconnected. Export checks recognize available copies.
Develop edits, masks, variants, original comparisons, detail views and exports use the same image identities and histories while offline. All source pixels remain available, so export dimensions and formats are unchanged. Export's Copy original option can use the verified working copy and keeps the original filename. Edits already belong to the catalog: reconnecting the drive does not require transferring an edit history.
Use Remove Offline Copies of Selection to reclaim space. Removal affects all variants of each selected source. OmaRAW requires a readable original with the saved SHA-256 before removing a copy. A disconnected, changed or damaged original is insufficient. A symlink back into the working-copy store is also insufficient. Originals are never deleted by these commands. If the working copy is damaged but the matching original is available, Keep Selection Available Offline rebuilds it.
Storage and recovery
Copies live in engine-library.db.offline/ beside the engine database in
the catalog's data directory. This is persistent application data, separate
from the preview cache. OmaRAW does not evict these files automatically.
Its index.json maps original paths to copy filenames, sizes and SHA-256s.
Renaming or relinking through OmaRAW updates that mapping without copying
the RAW again.
Copies are streamed into temporary files, flushed, checked by reading them back, then published under unique names. The index is replaced atomically. Cancellation and transfer failures retain the original and any earlier copy. A failed index write can leave a complete unreferenced file in the store; it is retained for recovery instead of being silently discarded. An unreadable or unsupported index is preserved and disables mutations.
The engine verifies a working copy before its first use after a restart. It rechecks after file identity, size or nanosecond modification/change timestamps differ. A failed check prevents processing from that copy, including exporting a frame already held in memory. Repeated processing of an unchanged verified copy avoids rehashing every pipeline stage.
Catalog backup bundles contain the edits and configuration, but do not
include these full-size working copies or original photos. Back up photos
separately. To preserve offline availability while moving a catalog, also
copy its complete engine-library.db.offline/ directory.
These are full-quality offline originals. Smart Previews provide a separate, smaller source for offline editing. Full copies take precedence over Smart Previews and continue to support full-quality export.
Smart Previews
Smart Previews keep a smaller editable source beside your catalog so you can work with the original drive disconnected. They contain no baked-in Develop adjustments. Your edits, masks, variants and snapshots stay in the same catalog and apply to the original when it is available again.
Build and use
- Select photos in Library.
- Choose Library → Smart Previews → Build Smart Previews for Selection.
- Wait for the status line to report completion before disconnecting the drive.
Alternatively, enable Build Smart Previews after import in the Import browser. The choice is remembered. Previews are built for newly imported photos; files skipped as duplicates can be selected and built through Library. An import can queue its preview work behind another offline job.
Library's inspector shows the preview dimensions and disk space. Develop shows Editing Smart Preview when the original and full offline copy are unavailable. OmaRAW checks the current photo's source availability every two seconds while idle and switches back automatically when the drive returns.
The source order is: readable original, verified full offline copy, verified Smart Preview. Variants share one preview. Crop, colour, masks and history remain editable; 100% shows the preview's available pixels. Fine detail, noise and RAW reconstruction can look different at reduced resolution. Sensor-clipping inspection requires the full source.
Exports and full-quality prints require the original or a full offline copy. OmaRAW reports a reconnect message rather than exporting from the reduced source. Thumbnail contact sheets remain available as before.
Storage and removal
Previews are at most 2560 pixels on the long edge. RAW previews preserve a reduced sensor mosaic and camera metadata. RGB sources retain reduced, unedited RGB pixels and their embedded colour profile. Compression is lossless after downsampling; the file size depends on the source. Large RAW files usually shrink substantially, while an already compressed JPEG or a simple PNG can be smaller than its editable preview.
The files live in engine-library.db.smart-previews/ beside the engine database. They are persistent, separate from the disposable thumbnail cache, and are not automatically evicted. A preview is shared by every variant of its original. Renaming or relinking through OmaRAW updates its reference.
Choose Library → Smart Previews → Discard Smart Previews of Selection to reclaim space. A matching original or verified full offline copy must be available. Discarding does not delete originals or edits. Cancel stops the remaining job and retains completed previews.
Catalog backup bundles currently contain edits/configuration/imported masks, not Smart Preview files. To retain offline availability while moving or restoring a catalog, also copy its complete smart-previews directory. Always back up originals separately: reduced previews cannot replace them.
Limits and recovery
Interrupted preview creation leaves the originals and completed previews intact. Missing or damaged previews can be rebuilt when the matching original or full offline copy is connected. If an original's contents have changed, OmaRAW reports that instead of silently replacing its preview.
Not every RAW format can be reduced into a Smart Preview. Some compressed RAWs and four-colour sensors require a full offline copy. A camera's embedded JPEG preview can be visible even when its RAW data cannot be decoded. A full offline copy preserves the complete file; it cannot add support for an unsupported camera.