NMDA DB2 snapshot backups hanging
Summary: DB2 snapshot backups hanging
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Symptoms
NMDA DB2 snapshot backups hanging
DB2 DB is write suspend mode
Error in db2diag.log
Warning:
----------------------------------------
2016-05-20-15.05.16.771114+000 E7423877A808 LEVEL: Warning
PID : 7733668 TID : 47390 PROC : db2sysc 0
INSTANCE: <instance_name> NODE : 000 DB :
APPHDL : 0-57647 APPID: <app_id>
AUTHID :
EDUID : 47390 EDUNAME: db2agent (instance) 0
FUNCTION: DB2 UDB, database monitor, sqm___sqlmonssagnt, probe:1234
DATA #1 : <preformatted>
This occurs when any snapshot other than list applications is attempted
on a database that is write suspended. This is necessary due to latching
conflicts. This database is skipped in the snapshot, but other databases
should still be processed. Skipping database '<db_name>'.
For more information on write suspend, please see the
'db2 set write suspend for database' command.
------------------------------------------
Cause
DB2 workflow works as:
DB2 calls db2ACSPrepare() in NMDA DB2 library to do initial preparation to get ready for the hardware snapshot. Once this is done, DB2 Database manager suspends the database and calls NMDA DB2 funtion db2ACSSnapshot(). In this case, DB2 does not call db2ACSSnapshot(). The workflow stops and hangs for DB2 engine to continue the backup. IBM support PMR: 29538,004,000 is opened. IBM DB2 engineering needs more debug to determine the root cause of this hanging.
DB2 calls db2ACSPrepare() in NMDA DB2 library to do initial preparation to get ready for the hardware snapshot. Once this is done, DB2 Database manager suspends the database and calls NMDA DB2 funtion db2ACSSnapshot(). In this case, DB2 does not call db2ACSSnapshot(). The workflow stops and hangs for DB2 engine to continue the backup. IBM support PMR: 29538,004,000 is opened. IBM DB2 engineering needs more debug to determine the root cause of this hanging.
Resolution
Workaround:
- Cancel current backup
- Take DB out of write suspend mode
In order to discover the root cause, IBM DB2 support requests following info for further investigation,
1. Delete/relocate any stacks/dumps in db2dump directory. It creates new stacks/dumps without mixing old ones. (Unix/Linux path: /$INSTHOME/sqllib/db2dump)
2. DB2 trace for a short while:
db2trc on -f trace.dmp
wait about 30 seconds
db2trc off
db2trc fmt trace.dmp trace.fmt
db2trc flw trace.dmp trace.flw
3. Gather stacks:
db2pd -stack all -rep 5 5
4. When step 3) completes, run,
procstack <PID> > db2vend.pstack.out
The <PID> is the Process ID of the db2vend process for the database.
5. Then get the snapshot backup session,
db2 get snapshot for applications on <dbname> > db2snap.out
6. Now you can set write resume, and then try the snapshot backup again and see if it finishes.
7. Gather a db2support.zip as follows:
db2support . -d <dbname> -c -s
8. Zip and send to IBM PMR:
trace.dmp
trace.fmt
trace.flw
db2vend.pstack.out
db2snap.out
db2support.zip
- Cancel current backup
- Take DB out of write suspend mode
In order to discover the root cause, IBM DB2 support requests following info for further investigation,
1. Delete/relocate any stacks/dumps in db2dump directory. It creates new stacks/dumps without mixing old ones. (Unix/Linux path: /$INSTHOME/sqllib/db2dump)
2. DB2 trace for a short while:
db2trc on -f trace.dmp
wait about 30 seconds
db2trc off
db2trc fmt trace.dmp trace.fmt
db2trc flw trace.dmp trace.flw
3. Gather stacks:
db2pd -stack all -rep 5 5
4. When step 3) completes, run,
procstack <PID> > db2vend.pstack.out
The <PID> is the Process ID of the db2vend process for the database.
5. Then get the snapshot backup session,
db2 get snapshot for applications on <dbname> > db2snap.out
6. Now you can set write resume, and then try the snapshot backup again and see if it finishes.
7. Gather a db2support.zip as follows:
db2support . -d <dbname> -c -s
8. Zip and send to IBM PMR:
trace.dmp
trace.fmt
trace.flw
db2vend.pstack.out
db2snap.out
db2support.zip
Affected Products
NetWorker Module for Databases and ApplicationsProducts
NetWorker Module for Databases and ApplicationsArticle Properties
Article Number: 000056670
Article Type: Solution
Last Modified: 30 May 2024
Version: 3
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