LO_Base(JRE) tables missing

Pi3 Raspbrian debian 10 (buster)
LibreOffice Version: 6.1.5.2

i am very dedicated to learning how this may have occurred
because i never want to do this again !

[ sorry this is long but many people that reply to questions,
mention the lack of details provided in the questions asked.
please read on because after all the effort to understand the causes,
it remains unclear what may have lead to the loss of tables. ]

after a successful new install of the above OS & Application,
i created 6 tables (approx. 100 records per table) to learn about Base.
for several days i was able to create, edit & view using HSQLDB.
a week later i clicked on the “Tables” icon and receive the famous
JRE error msg. - Please install a JRE and restart LibreOffice.

having min. knowledge of Java and no idea what JDK or JRE even was,
i have now spent 2 weeks reading 100’s of postings on half dozen forums,
i now feel i have enough information to ask a question.

i was not aware of what version of JRE was installed at the time of the failure
but during the long process of trouble shooting in Tools>Options>Advanced
i think i recall seeing a version # something like 1.8.???180 but i could be mistaken
because i may have seen a screenshot from one of the many ‘how to fix’ tutorials.
googling for hours and searching java sites for days looking for vintage versions,
i failed to find what i thought was installed.

the reason for the extensive search is because i was attempting to locate the version of JRE
that was working before the system began reporting the lack of a JRE.
so as shown below i have installed several versions of JRE and while i can now use LO_Base
(create, edit & view NEWER tables) none of these versions allow access to the original tables i first created.


Q1: is there an explanation as to why my original tables can not be seen/ are the tables truly missing ?

Q2: after getting a few JRE installed and trying each one at a time, why are there only 2 that appear under
Tools>Options>Advanced ?

Oracle Corporation 10.0.2
&
Oracle Corporation 1.8.0_212

Q3: why is not possible to use the “Add” button within the Java Options window to load a JRE following the
paths to the installed JRE as shown below ?

THESE ARE THE 5 CURRENTLY INSTALLED JRE
Path Priority Status

0 /usr/lib/jvm/java-11-openjdk-armhf/bin/java 1111 auto mode

1 /home/pi/java/jdk1.8.0_212/bin/java 1 manual mode

2 /usr/lib/jvm/adoptopenjdk-8-hotspot-armhf/bin/java 1081 manual mode

3 /usr/lib/jvm/java-10-openjdk-armhf/bin/java 1101 manual mode

4 /usr/lib/jvm/java-11-openjdk-armhf/bin/java 1111 manual mode

5 /usr/lib/jvm/java-8-openjdk-armhf/jre/bin/java 1081 manual mode

Hello,

There is no way to determine based on your post why the tables went missing. HSQLDB embedded has had problems over the years and is partially why Firebird embedded is being implemented.

Know nothing about Pi3 Raspbrian. However on Ubuntu 18.04, for openjdk the location to point at is:

/usr/lib/jvm/java-11-openjdk-amd64

So would guess yours would be:

/usr/lib/jvm/java-11-openjdk-armhf

Do not know, without going through all the steps, why you have only two. On all my Linux systems (provided the correct Java was installed) have not had a problem with many different versions of Oracle JRE, JDK or OpenJDK.