Bug 28697526 - Session Hangs On 'gc cr request' And Other Sessions Wait On 'cr request retry' (Doc ID 28697526.8)

Bug 28697526  Session Hangs On 'gc cr request' And Other Sessions Wait On 'cr request retry'

Affects:

Product (Component)	Oracle Server (Rdbms)
Range of versions believed to be affected	Versions BELOW 20.1
Versions confirmed as being affected	18.3.0
Platforms affected	Generic (all / most platforms affected)

Fixed:

The fix for 28697526 is first included in

20.1.0 19.9.0.0.DBRU:201020 (OCT 2020) DB Release Update Revision(DB RU) 18.12.0.0.DBRU:201020 (OCT 2020) DB Release Update Revision(DB RU) 12.2.0.1.201020 (Oct 2020) Database Release Update (DB RU)  12.2.0.1.201020 (OCT 2020) Bundle Patch for Windows Platforms

Interim patches may be available for earlier versions - click here to check.

Description

A session hung waiting for wait event 'gc cr request', and it blocked
other sessions at wait event 'cr request retry'.
 
Rediscovery Notes
If a session hangs on 'gc cr request' but there are no blockers then you may have encountered this problem. 
 
Specifically:
 
- Long gc cr request wait
- GCS CLIENT: grant 0 cvt 1 mode 0x0 role 0x24...
- GCS CLIENT: KJBL history 0x1
- GCS SHADOW: grant 0 cvt 1 mode 0x0 role 0x2#...lst 0xc0 
 

 
Workaround
 
Set the parameter _gc_cr_server_read_wait=false.  Example:
 
alter system set "_gc_cr_server_read_wait"=false scope=both sid='*' ;
 

References

Bug:28697526 (This link will only work for PUBLISHED bugs)
Note:245840.1 Information on the sections in this article