SD-card/OSCAR losing data?

[Samultra]

Hi all, using Dreamstation Auto CPAP all nights; very successful therapy: AHI's well under 5
Each morning I pull my SD-card and stick it into my PC, run OSCAR 1.2.0 and Bingo: positive feedback from my results.

This morning though I looked at last night's data together, as it happened with my wife and were happy with my data, showing full data, a.o. 8½ hours of peaceful sleep AHI 1,57 I remember.
At the next OSCAR start 15 minutes  later however the nights' data had all disappeared BUT for Session END Times and Session START times. "There is no session to Graph - Sessions all off! "
WELCOME screen saying:  You only had the mask on for 0 hours, 0 minutes and 0 seconds.
You had an AHI of nan, which is equal to your 7 day average of 2.71.

All other data going back 4 years is there in OSCAR, fully retrievable, comprising of two different DreamStations. So no data loss on my PC.

Unplugging/plugging my SD-card did not reproduce data. 
Running CHKDSK on the SD-card gave no errors, no repairs.
Re-importing SD-card data (SHIFT F2) resulted in:  "Up to date".  
Inserted the SD-card in DreamStation: all indications normal.

Card's 2 GB is not full: contains 7.4 MB of data from 17feb21 back to 17dec20; apparently 2 months of rolling data. 
Inspecting SD-card contents using TreeSize shows last accessed 17feb21 (today) and a regular chronological  folder/file pattern including Archives, LOG SEQ and PROP.txt files, filled with non-comprehensible database-data characters.

I remember I had this occurrence once before within the last 2 months running; apparently solved as I see no other blank days...

A self-healing glitch?

More detail available obviously. 

Anyone out there with similar omissions that appear after viewing todays'/last nights' data? Any clues?
Looking forward to your responses,
Sam

PS SD-card is permanently UN-locked using tape hack

[Crimson Nape]

Here are 2 things you can try.  They are not listed in any certain order.  Pick one to try and see if it fixed your problem before going to the next one.  

1. Purge the day's data that is incomplete and then reimport it.
   
2. Select Data ⇾ Rebuild CPAP Data ⇾ Your CPAP Model
   

[Samultra]

Hi Crimson thx forcresponding.
I am ICT savvy but -  What is PURGE in this context? Where is the purge button?
On the SD-card? On my PC? 
Ciao
Sam

[Crimson Nape]

Data ⇾ Advanced ⇾ Purge Current Selected Day.    Make sure that you have the day you wish to purge displayed in your Daily screen.    My signature has a link, Beginner's Guide to Sleepyhead and OSCAR, to the user's guide for OSCAR and its predecessor, SleepyHead.   Reviewing this document should prove helpful in using and understanding OSCAR and its options.

[Samultra]

Hi Crimson,

your suggestion did the trick! Wonderful.

All data up to last night's - this morning's 18feb21 are back there again in good order

Meanwhile I have been trying to understand this PURGE mechanism - what exactly does it do, how does it restore apparently missing data?
Could you point me to a reference article perhaps?

Thank you for your kind help,

Regards
Sam

[A KLERK]

OSCAR stores an incremental backup of all raw data under the profiles folder. So, in order to repair the database with interpreted data (for instance after an update or mishap/crash) this database can be deleted and again filled from the backup. 
The only two things to keep in mind are:

1. Is there really a backup? ResMed stores only a limited time of high res data, so one should port at least one ever two weeks
   
2. Far in the past, some machines did not make a backup, or a user has switched that option off in Preferences. 
   

So, never ever delete the OSCAR_Data folder, as you will lose the backup that's in it...

[A KLERK]

The former story is for rebuilding the entire database. But your question was about purging a single day. 
That is an option to delete the data of the night visible in Daily view. Helpful if somebody made a mistake during import, or imported and then slept again before noon. OSCAR will not import the same day again, so that must be purged before importing it again. 
I hope this is clear enough...

[Samultra]

Good morning A Klerk -

"OSCAR will not import the same day again, so that must be purged before importing it again. I hope this is clear enough..."
That explains it all; a matter of definitions.

Being an old hand (74) in ICT "purging" sounds utterly destructive to me, as in 

PURGE defined

So I would normally be very cautious to perform a purge.

Ciao,
Sam