Update on ACT_RU_EXECUTION

Hi,
I’m using flowable with an Oracle database and I´m having an issue on the following query:

update ACT_RU_EXECUTION set LOCK_TIME_ = :1 where ID_ = :2 and (LOCK_TIME_ is null OR LOCK_TIME_ < :3 )

It says:

The SQL statement with SQL_ID “ab46ty50gvtw4” was blocked on row locks.

The SQL_ID shows the previous update query.

In my research, I found that this error occurs when two or more sessions want simultaneous access to a resource.
Are there some changes in the schema for Oracle databases?
What situation could be triggering this error?

This particular update happens when a a job gets executed and it needs to have a lock on the process instance due to being an exclusive job.

We haven’t heard of this problem yet on Oracle. Which Oracle version are you using? Which isolation level?

One option would be to add/remove indexes on the LOCK_TIME … but want to understand first why this would be a problem for a database.