CTWR blocking either DBWR, CKPT or LGWR and causing DB hang (Doc ID 2297251.1)

Last updated on SEPTEMBER 01, 2017

Applies to:

Oracle Database - Enterprise Edition - Version 11.2.0.1 and later
Information in this document applies to any platform.
Database hang; hanganalyze shows the CTWR process is blocking either the DBWR, CKPT or LGWR (some write activity)



Symptoms

Database is hanging.  Hang analyze shows the CTWR process is blocking either the DBWR, CKPT or LGWR (some write activity).  The CTWR process itself does NOT show as being blocked and shows no unusual or slow waits.  Typical waits seen in a hanganalyze would be:

and is blocked by

=> Oracle session identified by:
{
os id: 48288
process id: 126, oracle@hostname (CTWR)
session id: 1891
session serial #: 1
}
which is not in a wait:
{
last wait: 0.000000 sec ago
blocking: 1 session
current sql: <none>
short stack: ksedsts()+465<-ksdxfstk()+32<-ksdxcb()+1927<-sspuser()+112<-__sighandler()<-krcclhc()+714<-krccahc()+9<-krccchk()+23<-krccppu()+335<-krccioc()+308<-krccwio()+296<-krccgb()+217<-krccread()+88<-krcchg()+752<-krcptmo()+862<-ksbcti()+513<-ksbabs()+1735<-krcpabs()+855<-ksbrdp()+1045<-opirip()+623<-opidrv()+603<-sou2o()+103<-opimai_real()+250<-ssthrdmain()+265<-main()+201<-__libc_start_main()+245
wait history:
1. event: 'db file sequential read'
time waited: 0.001083 sec
wait id: 7934128 p1: 'file#'=0x247
p2: 'block#'=0x36df00
p3: 'blocks'=0x1
* time between wait #1 and #2: 0.002384 sec
2. event: 'db file sequential read'
time waited: 0.000571 sec
wait id: 7934127 p1: 'file#'=0x247
p2: 'block#'=0x36df00
p3: 'blocks'=0x1
* time between wait #2 and #3: 0.005047 sec
3. event: 'db file sequential read'
time waited: 0.000655 sec
wait id: 7934126 p1: 'file#'=0x2ad
p2: 'block#'=0x378f00
p3: 'blocks'=0x1
}

Note: the callstack may vary and is not deterministic for this issue

 

Changes

 Block change tracking is in use.

Cause

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