The below error message is very common and users see in alert<SID> .log file. You will see this error message when writing the redo info is not completed, when the log switch happens.
Note that the log switch cannot happen until all of the redo has been written.
Users might also notice these error messages when there is an issue with network or storage where you have archive log destination, this is due to delay or hand in LGWR switch .
Thread 1 cannot allocate new log, sequence 5929
Private strand flush not complete
Current log# 4 seq# 5928 mem# 0: /oracle/ORAC/origlogB/log_g14m1.dbf
Current log# 4 seq# 5928 mem# 1: /oracle/ORAC/mirrlogB/log_g14m2.dbf
Beginning log switch checkpoint up to RBA [0x10189.2.10], SCN: 6845363020
Thread 1 advanced to log sequence 5929 (LGWR switch)
This message related to internal Cache Redo File management and safe to discard these messages.
These messages are not cause for concern unless there is a significant time gap between “cannot allow new log” and “advanced to log sequence” message. In some cases users benefited with db_writer_processes and this help to avoid message from being generated.
Click here to learn about "Cannot allocate new log & Checkpoint not complete"
message in alert.log
Satishbabu Gunukula, Oracle ACE