Hi Christian,

thanks a lot for your advice.

Following brought some further insights.

I backed up the database and then tried to optimize it, without and with the all option.

However, this led to the following error message (prompt shown as $):

$ xquery db:optimize("cap10_cap_store_prod")
[db:lock] Database 'cap10_cap_store_prod' is currently opened by another process.

However, this database shouldn’t be used by any process any longer. We created a new one with a different name.

SHOW SESSIONS did not reveal any sessions.

Reading the BaseX (https://docs.basex.org/wiki/Transaction_Management#File-System_Locks) we found out that there are two kinds of file-system locks:

1. Update Operations
2. Database Locks

I did not found any upd.basex file in the data directory, so I assume it is a database lock.

Is there any way to remove this lock, like a force option of the optimize command or a dedicated command?

Is it possible to force close/kill the dangling session/process? As I said I’m pretty sure there isn’t any process accessing this database, but still the database is in the locked state. Probably the process and/or db was shut down in an ungraceful way. How can such a situation be handled? We have to assume that this could possibly happen again and need a strategy to deal with it.

I could also pin down the moment when it happened in the log file. There is a strange character sequence in the log file, and after that all the attempted operations fail:

103537 15:46:02.721    127.0.0.1:33919 admin   OK      Query executed in 3.36 ms.      3.42 ms
 103538 15:46:02.724    127.0.0.1:40847 admin   OK      Query executed in 9.32 ms.      9.4 ms
 103539 15:46:02.956    127.0.0.1:40847 admin   REQUEST XQUERY db:open('cap10_cap_store_prod', 'dfade903-4365-44ce-a0dc-abbe474a7daa.cap')      0.08 ms
 103540 15:46:02.962    127.0.0.1:40847 admin   OK      Query executed in 6.07 ms.      6.15 ms
 103541 ^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@16:13:26.567    127.0.0.1:40847 admin   REQUEST ADD TO 003843e7-47ef-4a58-be8b-b7d6e665bbb1.cap [...]   0.11 ms
 103542 16:13:26.583    127.0.0.1:40847 admin   ERROR   Improper use? Potential bug? Your feedback is welcome: Contact: basex-talk@mailman.uni-konstanz.de Version: BaseX 9.0.1 Java: Debian, 11.0.9 OS: Linux, amd64 Stack Trace: java.lang.RuntimeException: cap10_cap_store_prod: lock file does not exist. at org.basex.util.Util.notExpected(Util.java:61) at org.basex.data.DiskData.finishUpdate(DiskData.java:246) at org.basex.core.cmd.ACreate.update(ACreate.java:97) at org.basex.core.cmd.Add.run(Add.java:56) at org.basex.core.Command.run(Command.java:257) at org.basex.core.Command.execute(Command.java:93) at org.basex.core.Command.execute(Command.java:116) at org.basex.server.ClientListener.execute(ClientListener.java:343) at org.basex.server.ClientListener.add(ClientListener.java:314) at org.basex.server.ClientListener.run(ClientListener.java:96)   15.75 ms

The error admin ERROR Improper use? Potential bug?keeps repeating from then on. Do you see anything unusual, or can any insights be gained from these logs?

Any help in solving this issue is greatly appreciated.

Kind regards,
Thomas

On 4 Jan 2021, at 9:20, Christian Grün wrote: