Oracle Course archive, day 12th

The deadlock is due to the fact that two objects request another resource with one resource,

Another resource happens to be holding the two objects, causing the two objects to be unable to complete the operation, and the resources held cannot be freed.

Blocking is a queued wait phenomenon caused by insufficient resources.

UNSO: Undo

Commit: Submit

Contents: Content

Management: Management

Session: A connection is a conversation
Represents a scope.
That is, some modifications can be limited to this session, not in other sessions

AM: 11:59

PM: 12:00

Global support

Unset: Not set

Profile: Contour

Deadlock:
Session1:
Sql> select * from T1;

X
----------
1
2
sql> Update T1 set x=11 where x=1;
Session2:
sql> Update T1 set x=22 where x=2;
Session1:
sql> Update T1 set x=222 where x=2; blocking
Session2:
sql> Update T1 set x=111 where x=1; deadlock
ERROR at line 1:
Ora-00060:deadlock detected while waiting for resource
$ vi/u01/app/oracle/diag/rdbms/orcl/orcl/trace/alert_orcl.log

Locks and foreign keys
Select ... for update

Global support
$ VI. bash_profile
#export Nls_lang=american_america. Al32utf8
#export nls_date_format= ' Yyyy-mm-dd hh24:mi:ss '
$ unset Nls_lang
$ unset Nls_date_format
Sql> select Sysdate from dual;

Oracle Course archive, day 12th