ORA-08177: can't serialize access for this transaction about relstorage HOT 4 CLOSED

Sorry for the trouble. I have to tell you that Oracle+RelStorage is barely supported and not regularly tested. If possible, I encourage people to migrate to PostgreSQL 11+.

However if I start Plone a second time it works without a problem

Do you mean, you stop plone and just start it again? Or you start a second instance? I'm not sure what difference it makes because I don't know why you would be getting this.

Once you start a second instance, the trouble disappears for good?

ORA-08177: can't serialize access for this transaction

IIRC, the error you're getting means that there are multiple transactions in progress that conflict. I don't know enough about Zope/Plone startup to guess why that would be. Normally I wouldn't expect that. Perhaps you're starting multiple worker processes at the same time?

Especially here, when it's just trying to load the root object conn.get(z64).

Googling suggests that this may be a problem related to particular versions of Oracle and how it handles the undo segments. If that's the case, simply connecting to the database from a single client (ZODB.config.open(…)) before attempting to start multiple processes/threads ought to initialize the rollback segments and solve the issue.

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I start just one instance (./bin/client1 fg), nothing more. However I think one client usually spawns multiple worker threads.
I am assuming that the error only happens while the database is created. After that it works normal.

We have a customer who wishes to use its Oracle database, so we do it with our application. I don't think we can switch to an other database backend now. For other projects we usually use Postgres as well.

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I am assuming that the error only happens while the database is created. After that it works normal.

I don't know what to suggest, other than what I suggested before (open a "pre-flight" connection).

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Closing; no updates since 2021.

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