We ran out of cursors on our RAC installation recently and were seeing v$session with Active status and username blank. there were some active connections with username but rest were all blank.
We are puzzled on how null username became an active session, could be guess this to be an attempt to connect to database with blank username, would session stay active after that for some time?
See output of sqls below , see large number of connections with username=blank and TYPE=user and from a remote address.
SQL> select username,type,machine,count(*) from v$session group by username,type,machine;
USERNAME TYPE MACHINE COUNT(*)
------------------------------ ---------- ---------------------------------------------------------------- ----------
USER <obfuscated_remote_machine_addr> 146
USER <obfuscated_remote_machine_addr> 87
USER <obfuscated_remote_machine_addr> 152
USER <obfuscated_remote_machine_addr> 95
USER <obfuscated_remote_machine_addr> 49
USER <obfuscated_remote_machine_addr> 127
USER <obfuscated_remote_machine_addr> 138
USER <obfuscated_remote_machine_addr> 92
USER <obfuscated_remote_machine_addr> 159
USER <obfuscated_remote_machine_addr> 85
APPLICATION_USER USER <obfuscated_remote_machine_addr> 2
SYS USER <obfuscated_remote_machine_addr> 7
APPLICATION_USER USER <obfuscated_remote_machine_addr> 1
PUBLIC USER <obfuscated_remote_machine_addr> 5
PUBLIC BACKGROUND <obfuscated_remote_machine_addr> 2
APPLICATION_USER USER <obfuscated_remote_machine_addr> 2
APPLICATION_USER USER <obfuscated_remote_machine_addr> 2
APPLICATION_USER USER <obfuscated_remote_machine_addr> 1
APPLICATION_USER USER <obfuscated_remote_machine_addr> 1
USER <obfuscated_remote_machine_addr> 162
USER <obfuscated_remote_machine_addr> 101
USER <obfuscated_remote_machine_addr> 168
USER <obfuscated_remote_machine_addr> 157
USER <obfuscated_remote_machine_addr> 22
USER <obfuscated_remote_machine_addr> 101
USER <obfuscated_remote_machine_addr> 141
USER <obfuscated_remote_machine_addr> 86
USER <obfuscated_remote_machine_addr> 147
USER <obfuscated_remote_machine_addr> 17
USER <obfuscated_remote_machine_addr> 18
APPLICATION_USER USER <obfuscated_remote_machine_addr> 2
APPLICATION_USER USER <obfuscated_remote_machine_addr> 2
APPLICATION_USER USER <obfuscated_remote_machine_addr> 2
APPLICATION_USER USER <obfuscated_remote_machine_addr> 2
APPLICATION_USER USER <obfuscated_remote_machine_addr> 3
PUBLIC USER <obfuscated_remote_machine_addr> 2
APPLICATION_USER USER <obfuscated_remote_machine_addr> 1
APPLICATION_USER USER <obfuscated_remote_machine_addr> 1
APPLICATION_USER USER <obfuscated_remote_machine_addr> 1
APPLICATION_USER USER <obfuscated_remote_machine_addr> 2
USER <obfuscated_remote_machine_addr> 75
USER <obfuscated_remote_machine_addr> 138
USER <obfuscated_remote_machine_addr> 128
USER <obfuscated_remote_machine_addr> 89
USER <obfuscated_remote_machine_addr> 160
USER <obfuscated_remote_machine_addr> 158
USER <obfuscated_remote_machine_addr> 150
USER <obfuscated_remote_machine_addr> 122
USER <obfuscated_remote_machine_addr> 63
USER <obfuscated_remote_machine_addr> 47
USER <obfuscated_remote_machine_addr> 136
USER <obfuscated_remote_machine_addr> 71
USER <obfuscated_remote_machine_addr> 14
APPLICATION_USER USER <obfuscated_remote_machine_addr> 1
APPLICATION_USER USER <obfuscated_remote_machine_addr> 3
APPLICATION_USER USER <obfuscated_remote_machine_addr> 1
APPLICATION_USER USER <obfuscated_remote_machine_addr> 1
APPLICATION_USER USER <obfuscated_remote_machine_addr> 2
APPLICATION_USER USER <obfuscated_remote_machine_addr> 1
APPLICATION_USER USER <obfuscated_remote_machine_addr> 3
APPLICATION_USER USER <obfuscated_remote_machine_addr> 1
USER <obfuscated_remote_machine_addr> 148
USER <obfuscated_remote_machine_addr> 153
USER <obfuscated_remote_machine_addr> 12
USER <obfuscated_remote_machine_addr> 70
USER <obfuscated_remote_machine_addr> 127
USER <obfuscated_remote_machine_addr> 41
USER <obfuscated_remote_machine_addr> 147
USER <obfuscated_remote_machine_addr> 142
USER <obfuscated_remote_machine_addr> 152
APPLICATION_USER USER <obfuscated_remote_machine_addr> 2
PUBLIC USER <obfuscated_remote_machine_addr> 7
APPLICATION_USER USER <obfuscated_remote_machine_addr> 2
USER <obfuscated_remote_machine_addr> 1
APPLICATION_USER USER <obfuscated_remote_machine_addr> 1
APPLICATION_USER USER <obfuscated_remote_machine_addr> 1
USER <obfuscated_remote_machine_addr> 163
USER <obfuscated_remote_machine_addr> 140
USER <obfuscated_remote_machine_addr> 137
USER <obfuscated_remote_machine_addr> 148
USER <obfuscated_remote_machine_addr> 142
USER <obfuscated_remote_machine_addr> 131
USER <obfuscated_remote_machine_addr> 151
USER <obfuscated_remote_machine_addr> 12
USER <obfuscated_remote_machine_addr> 152
USER <obfuscated_remote_machine_addr> 155
USER <obfuscated_remote_machine_addr> 148
USER <obfuscated_remote_machine_addr> 154
USER <obfuscated_remote_machine_addr> 17
USER <obfuscated_remote_machine_addr> 20
APPLICATION_USER USER <obfuscated_remote_machine_addr> 3
APPLICATION_USER USER <obfuscated_remote_machine_addr> 1
APPLICATION_USER USER <obfuscated_remote_machine_addr> 7
APPLICATION_USER USER <obfuscated_remote_machine_addr> 4
APPLICATION_USER USER <obfuscated_remote_machine_addr> 2
APPLICATION_USER USER <obfuscated_remote_machine_addr> 1
APPLICATION_USER USER <obfuscated_remote_machine_addr> 2
USER <obfuscated_remote_machine_addr> 143
USER <obfuscated_remote_machine_addr> 148
USER <obfuscated_remote_machine_addr> 145
USER <obfuscated_remote_machine_addr> 179
USER <obfuscated_remote_machine_addr> 149
USER <obfuscated_remote_machine_addr> 152
USER <obfuscated_remote_machine_addr> 143
USER <obfuscated_remote_machine_addr> 175
USER <obfuscated_remote_machine_addr> 130
APPLICATION_USER USER <obfuscated_remote_machine_addr> 2
APPLICATION_USER USER <obfuscated_remote_machine_addr> 5
APPLICATION_USER USER <obfuscated_remote_machine_addr> 2
APPLICATION_USER USER <obfuscated_remote_machine_addr> 3
APPLICATION_USER USER <obfuscated_remote_machine_addr> 6
APPLICATION_USER USER <obfuscated_remote_machine_addr> 2
USER <obfuscated_remote_machine_addr> 157
USER <obfuscated_remote_machine_addr> 134
USER <obfuscated_remote_machine_addr> 15
APPLICATION_USER USER <obfuscated_remote_machine_addr> 1
USER <obfuscated_remote_machine_addr> 17
APPLICATION_USER USER <obfuscated_remote_machine_addr> 2
USER <obfuscated_remote_machine_addr> 158
USER <obfuscated_remote_machine_addr> 67
APPLICATION_USER USER <obfuscated_remote_machine_addr> 2
APPLICATION_USER USER <obfuscated_remote_machine_addr> 1
APPLICATION_USER USER <obfuscated_remote_machine_addr> 2
APPLICATION_USER USER <obfuscated_remote_machine_addr> 1
PUBLIC USER <obfuscated_remote_machine_addr> 3
APPLICATION_USER USER <obfuscated_remote_machine_addr> 1
APPLICATION_USER USER <obfuscated_remote_machine_addr> 1
PUBLIC USER <obfuscated_remote_machine_addr> 8
USER <obfuscated_remote_machine_addr> 135
USER <obfuscated_remote_machine_addr> 157
USER <obfuscated_remote_machine_addr> 142
USER <obfuscated_remote_machine_addr> 143
USER <obfuscated_remote_machine_addr> 40
USER <obfuscated_remote_machine_addr> 142
USER <obfuscated_remote_machine_addr> 145
USER <obfuscated_remote_machine_addr> 126
USER <obfuscated_remote_machine_addr> 13
USER <obfuscated_remote_machine_addr> 113
USER <obfuscated_remote_machine_addr> 158
USER <obfuscated_remote_machine_addr> 18
USER <obfuscated_remote_machine_addr> 62
USER <obfuscated_remote_machine_addr> 68
USER <obfuscated_remote_machine_addr> 5
BACKGROUND <obfuscated_remote_machine_addr> 41
USER <obfuscated_remote_machine_addr> 58
USER <obfuscated_remote_machine_addr> 8
USER <obfuscated_remote_machine_addr> 78
PUBLIC USER <obfuscated_remote_machine_addr> 7
APPLICATION_USER USER <obfuscated_remote_machine_addr> 2
USER <obfuscated_remote_machine_addr> 20
APPLICATION_USER USER <obfuscated_remote_machine_addr> 1
APPLICATION_USER USER <obfuscated_remote_machine_addr> 3
APPLICATION_USER USER <obfuscated_remote_machine_addr> 2
APPLICATION_USER USER <obfuscated_remote_machine_addr> 1
APPLICATION_USER USER <obfuscated_remote_machine_addr>