shutdown immediate not going , backup fail

[yls177]

hi, my oracle db is not shutting down, hence backup was hanging. i have provided the logs as below. it comes irregularly. any advise? thanks


Shutting down instance (immediate)
License high water mark = 23

ORACLE V8.0.6.1.0 - Production vsnsta=0
vsnsql=c vsnxtr=3
Windows NT V4.0, OS V5.101, CPU type 586


also, a proper shutdown and backup successful will have these additional logs as below. but when it did not shutdown and backup successful, it is missing the below entries

ALTER DATABASE CLOSE NORMAL
SMON: disabling tx recovery
SMON: disabling cache recovery
Thread 1 closed at log sequence 14326
Completed: ALTER DATABASE CLOSE NORMAL
ALTER DATABASE DISMOUNT
Completed: ALTER DATABASE DISMOUNT