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Resolving DB Startup Failure Error Due to Duplicate Shared Memory Key (Shared Memory Key)

Document Type | Technical Information

Category | Monitoring/Inspection

Applicable Product Versions | 6FS05, 6FS06, 6FS07, 6FS07PS, 7FS01, 7FS02, 7FS02PS

Document Number | TMOTI034

 

Issue

When booting the DB, the error A shared memory segment with the same key already exists occurs and the startup fails.
ASCMD> cd archive
current path = +DS/archive
ASCMD> ls
<File_name>
log-t0-r0-s5.arc
 - Number of files found: 1


ASCMD> rm log-t0-r0-s5.arc
rm complete: +DS/archive/log-t0-r0-s5.arc --> archive deleted
ASCMD> ls

ERROR: no such path '+DS/archive/' (rc=-19)

 

Cause

When Tibero boots the DB, the shm key value is created by hashing $TB_HOME and $TB_SID to generate a unique shm key, then shared memory is created using that key.
 
If shared memory already exists with the same key and another process is attached to it, the A shared memory segment with the same key already exists error occurs and the DB startup fails.
 
Note that since the shm key is hashed from $TB_HOME and $TB_SID values, a simple restart does not resolve the issue.
 
 

Solutions

Check the SHM_KEY value recorded in the log, identify the corresponding shared memory shmid, then remove that shared memory segment and restart the DB to boot normally.
$  tbboot
**************************************************************
* A shared memory segment with the same key already exists.
* SHM_KEY = 0x1438469a
* Trying to reuse the shared memory segment....
**************************************************************

$ ipcs -m | awk '$1=="0x1438469a" {print $2}' | xargs ipcrm -m
--- '$1=="[Modify to match SHM_KEY value]"


$ tbboot
Listener port = 9292


Tibero 6


TmaxData Corporation Copyright (c) 2008-. All rights reserved.
Tibero instance started up (NORMAL mode).

Note

$ ipcs -m | awk '$1=="0x1438469a" {print $2}' | xargs ipcrm -m Explanation of command
  • ipcs -m : Lists shared memory resources
  • awk '$1=="0x1438469a" {print $2}' : Prints the second field of rows where the first field is 0x1438469a
  • xargs ipcrm -m : Removes shared memory using the passed argument
In summary, this command queries shared memory resources, selects the shared memory whose first field (key) matches 0x1438469a, obtains its second field (shmid), and removes it using ipcrm -m.
 
ipcs -m Additional explanation related to commands
  • ipcs -s : Lists semaphore resources
  • ipcrm -s : Removes semaphores

 

 

 

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