ORA-01545: rollback segment 'string' specified not available

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ORA-01545: rollback segment 'string' specified not available
Cause: Either: 1) An attempt was made to bring a rollback segment online that is
unavailable during startup; for example, the rollback segment is in an offline
tablespace. 2) An attempt was made to bring a rollback segment online that is
already online. This is because the rollback segment is specified twice in the
ROLLBACK_SEGMENTS parameter in the initialization parameter file or the
rollback segment is already online by another instance. 3) An attempt was made to
drop a rollback segment that is currently online. 4) An attempt was made to alter a
rollback segment that is currently online to use unlimited extents. 5) An attempt
was made to online a rollback segment that is corrupted. This is because the
rollback is specified in _corrupted_rollback_segments parameter in initialization
parameter file.Action: Either: 1) Make the rollback segment available; for example, bring an
offline tablespace online. 2) Remove the name from the ROLLBACK_SEGMENTS
parameter if the name is a duplicate or if another instance has already acquired the
rollback segment. 3) Bring the rollback segment offline first. This may involve
waiting for the active transactions to finish, or, if the rollback segment needs
recovery, discover which errors are holding up the rolling back of the transactions
and take appropriate actions. 4) Same as 3). 5) Remove the name from the _
corrupted_rollback_segments parameter.