{"id":1119,"date":"2026-04-16T11:46:57","date_gmt":"2026-04-16T09:46:57","guid":{"rendered":"https:\/\/anjo.pt\/keyword-oracle\/?p=1119"},"modified":"2026-04-16T11:46:57","modified_gmt":"2026-04-16T09:46:57","slug":"alter-system-kill-session-force-timeout-0-new-form-of-kill-immediate","status":"publish","type":"post","link":"https:\/\/anjo.pt\/keyword-oracle\/2026\/04\/16\/alter-system-kill-session-force-timeout-0-new-form-of-kill-immediate\/","title":{"rendered":"Alter system kill session “force timeout 0” ? new form of “kill immediate”?"},"content":{"rendered":"\n

The other day I saw that besides the catcon.pl, there is a catcon_kill_sess_gen.sql:<\/p>\n\n\n

\nls -1 $ORACLE_HOME\/rdbms\/admin\/catcon*\n\/u00\/app\/oracle\/product\/19.30.0\/rdbms\/admin\/catcon_kill_sess_gen.sql\n\/u00\/app\/oracle\/product\/19.30.0\/rdbms\/admin\/catcon.pl\n\/u00\/app\/oracle\/product\/19.30.0\/rdbms\/admin\/catcon.pm\n\/u00\/app\/oracle\/product\/19.30.0\/rdbms\/admin\/catconst.pm\n\/u00\/app\/oracle\/product\/19.30.0\/rdbms\/admin\/catcont.sql\n<\/pre><\/div>\n\n\n
When looking at this file, I noticed it kills catcon session using a “ALTER SYSTEM KILL SESSION ‘sid, serial#’ FORCE TIMEOUT 0”, except if on Oracle 12.1, where still does “IMMEDIATE” instead:<\/p>\n\n\n\n
\"\"<\/a><\/figure>\n\n\n\n
This new syntax “FORCE TIMEOUT x” is first described in Oracle AI 26ai DB documentation<\/a> (but it seems to work from version 12.2). Basically it theoretically allows the draining of sessions by setting a timeout until the session terminates some task, before killing it.<\/p>\n\n\n\n
There are two new elements here: “FORCE” and “TIMEOUT x”.<\/p>\n\n\n\n
What I understood from documentation is:<\/p>\n\n\n\n
When not using the “FORCE”  keyword, the two following commands behave the same way:<\/p>\n\n\n\n
ALTER SYSTEM KILL SESSION ‘sid, serial#’ IMMEDIATE <\/strong>= ALTER SYSTEM KILL SESSION ‘sid, serial#’ TIMEOUT 0<\/strong><\/p>\n\n\n\n
Basically, it instructs Oracle to terminate a session and roll back ongoing transactions, release all session locks, recover the entire session state, and return control to you immediately.<\/p>\n\n\n\n
With the “FORCE” keyword alone, it terminates the session like “IMMEDIATE”, however waiting first for a timeout of 5 seconds.<\/p>\n\n\n\n
With the “FORCE TIMEOUT 0”, then the connection is closed immediately, when there is some activity going on.<\/p>\n\n\n\n
Here a summary of what I observed:<\/p>\n\n\n\n
ALTER SYSTEM KILL SESSION command:<\/th>Kill idle session<\/th>Kill ongoing select<\/th><\/tr><\/thead>
… IMMEDIATE<\/td>Killer<\/strong>:
System altered.
Killed <\/strong>session: 
ORA-03135: connection lost contact
ORA-03114: not connected to ORACLE<\/td>		Killer<\/strong>:
ORA-00031: session marked for kill
Killed <\/strong>session:
ORA-00028: your session has been killed<\/td><\/tr>
… FORCE<\/td>Killer<\/strong>:
System altered.
Killed <\/strong>session: 
ORA-03135: connection lost contact
ORA-03114: not connected to ORACLE<\/td>		Killer<\/strong>:
System altered.
Killed <\/strong>session:
ORA-00028: your session has been killed<\/td><\/tr>
… TIMEOUT 0<\/td>Killer<\/strong>:
System altered.
Killed <\/strong>session:
ORA-00028: your session has been killed
ORA-01012: not logged on<\/td>		Killer<\/strong>:
ORA-00031: session marked for kill
Killed <\/strong>session:
ORA-00028: your session has been killed<\/td><\/tr>
… FORCE TIMEOUT 0;<\/td>Killer<\/strong>:
System altered.
Killed <\/strong>session: 
ORA-03135: connection lost contact
ORA-03114: not connected to ORACLE<\/td>		Killer<\/strong>:
System altered.
Killed <\/strong>session:
ORA-03113: end-of-file on communication channel<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n
Just for completion, if using “DISCONNECT SESSION” instead, then the session might just automatically failover if the parameters are correctly set.<\/p>\n\n\n\n
Le me know if you have other inputs.<\/p>\n","protected":false},"excerpt":{"rendered":"
The other day I saw that besides the catcon.pl, there is a catcon_kill_sess_gen.sql: When looking at this file, I noticed it kills catcon session using a “ALTER SYSTEM KILL SESSION ‘sid, serial#’ FORCE TIMEOUT 0”, except if on Oracle 12.1, where still does “IMMEDIATE” instead: This new syntax “FORCE TIMEOUT x” is first described in […]<\/p>\n","protected":false},"author":3,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[6,90],"tags":[],"class_list":{"0":"post-1119","1":"post","2":"type-post","3":"status-publish","4":"format-standard","6":"category-oracle","7":"category-oracle-ai-26ai","8":"czr-hentry"},"_links":{"self":[{"href":"https:\/\/anjo.pt\/keyword-oracle\/wp-json\/wp\/v2\/posts\/1119","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/anjo.pt\/keyword-oracle\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/anjo.pt\/keyword-oracle\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/anjo.pt\/keyword-oracle\/wp-json\/wp\/v2\/users\/3"}],"replies":[{"embeddable":true,"href":"https:\/\/anjo.pt\/keyword-oracle\/wp-json\/wp\/v2\/comments?post=1119"}],"version-history":[{"count":1,"href":"https:\/\/anjo.pt\/keyword-oracle\/wp-json\/wp\/v2\/posts\/1119\/revisions"}],"predecessor-version":[{"id":1121,"href":"https:\/\/anjo.pt\/keyword-oracle\/wp-json\/wp\/v2\/posts\/1119\/revisions\/1121"}],"wp:attachment":[{"href":"https:\/\/anjo.pt\/keyword-oracle\/wp-json\/wp\/v2\/media?parent=1119"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/anjo.pt\/keyword-oracle\/wp-json\/wp\/v2\/categories?post=1119"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/anjo.pt\/keyword-oracle\/wp-json\/wp\/v2\/tags?post=1119"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}