IBM Support

What's a sustained trap?

Technical Blog Post


Abstract

What's a sustained trap?

Body

In some cases, you may see an EDU traps (e.g. with signal 11), FODC_Trapxxxxx folder is created in db2dump, the corresponding application receives SQL1224N indicates its connection is forced off, but the subsequent application(s) can still make connections to the database.

From db2diag.log, you can find:

1. Trap Sustainability Criteria Checking = true

2016-06-02-11.57.40.871392+480 I5041137A562       LEVEL: Severe
PID     : 9633846              TID  : 13517       PROC : db2sysc 0
INSTANCE: db2inst1             NODE : 000         DB   : PROD
APPHDL  : 0-42162              APPID: 172.23.8.72.57806.160602042559
AUTHID  : ASAPS   
EDUID   : 13517                EDUNAME: db2agent (PROD) 0
FUNCTION: DB2 UDB, RAS/PD component, pdResilienceIsSafeToSustain, probe:800
DATA #1 : String, 37 bytes
Trap Sustainability Criteria Checking
DATA #2 : Hex integer, 8 bytes
0x0000000000001000
DATA #3 : Boolean, 1 bytes
true

2. Message indicates "EDU has been suspended"

2016-06-02-11.57.41.275190+480 E5097042A446       LEVEL: Severe
PID     : 9633846              TID  : 13517       PROC : db2sysc 0
INSTANCE: db2inst1             NODE : 000         DB   : PROD
APPHDL  : 0-42162              APPID: 172.23.8.72.57806.160602042559
AUTHID  : ASAPS   
EDUID   : 13517                EDUNAME: db2agent (PROD) 0 (suspended) 0
FUNCTION: DB2 UDB, RAS/PD component, pdSuspendEDU, probe:10
MESSAGE : EDU has been suspended

 

All above suggest a sustained trap happened. The sustaining of traps in general depends on many things. After a sustained trap, the connection associated with the trapping agent should be forced off and receive error, the sustained traps do not hold up any other work.

Note that db2stop force will not be able to force the last suspended agent and it will hang in early versions(i.e. DB2 V9.7 FixPack 2 or earlier FixPacks, V9.8 FixPack 3 or earlier FixPacks). If db2stop force is hanging it is working as designed in these versions - though it should timeout and kill db2sysc after start_stop timeout(default 10 minutes).

The instruction of "Recovering from sustained traps" is in Information center:

Recovering from sustained traps - V9.7
Recovering from sustained traps - V9.8
Recovering from sustained traps - V10.1
Recovering from sustained traps - V10.5
Recovering from sustained traps - V11.1

[{"Business Unit":{"code":"BU029","label":"Data and AI"}, "Product":{"code":"SSEPGG","label":"DB2 for Linux, UNIX and Windows"},"Component":"","Platform":[{"code":"PF025","label":"Platform Independent"}],"Version":"","Edition":""}]

UID

ibm13286761