IT29399: SLOW CONNECTION DUE TO CONFLICT ON SQLDBCONF (DATABASE CONFIGURATION FILE).

Db2 Version 11.1 Mod 4 Fix Pack 6 for Linux, UNIX, and Windows
Db2 Version 11.1 Mod 4 Fix Pack 6 for Linux, UNIX, and Windows

APAR status

• Closed as program error.

Error description

• Frequent updates to config parameters may cause db2agent to hit
  file sharing violation.
  Such a parameter could be MAXAPPLS on the automatic setting that
  is incremented when the limit is exceeded.
  db2agent is the agent servicing connection request and trying to
  increase max application.
  
  A sharing violation is encountered when updating the DB config
  file, then the config update will be delayed by at least 10
  seconds.
  
  Following entry will show up in db2diag.log:
  ----------------
  2019-03-31-21.49.44.270148-240 I29995A676           LEVEL:
  Warning
  PID     : 20775166             TID : 77619          PROC :
  db2sysc 0
  INSTANCE: db2inst1             NODE : 000           DB   :
  SAMPLE
  APPHDL  : 0-250                APPID:
  127.0.0.1.64210.190401014926
  AUTHID  : TESTER               HOSTNAME: testaix
  EDUID   : 96675                EDUNAME: db2agent (SAMPLE) 3
  FUNCTION: DB2 UDB, config/install, sqlf_openfile, probe:3072
  MESSAGE : File not found error was incorrectly detected as file
  successfully
            opened after multiple attempts.
  DATA #1 : String, 62 bytes
  /home/db2inst1/db2inst1/NODE0000/SQL00001/SQLDBCONF
  DATA #2 : signed integer, 4 bytes
  ---------------
  
  Conflicts in SQLDBCONF can occur in the following environments:
  - STMM is enabled and automatic DB config parameters that are
  tuned by it
  - low starting MAXAPPLS automatic value with large number of
  concurrent connections
  - Concurrent read / write operations on the DB config (e.g. GET
  DB CFG and UPDATE DB CFG)
  
  For example, one scenario that leads to this problem is when
  MAXAPPLS in database configuration is set to a very small
  number, while being AUTOMATIC.
  Each database connection tries to increase MAXAPPLS, resulting
  in file sharing violation in SQLDBCONF.
  The external symptom is the noticeable slowdown in database
  connections by at least 10 seconds.
  The db2diag.log will show a rapid series of messages, each
  trying to update MAXAPPLS, as shown below:
  
  2019-03-06-09.07.45.827897 I40970A536 LEVEL: Event
  <snipped...>
  EDUID : 1234 EDUNAME: db2agent (SAMPLE) 3
  FUNCTION: DB2 UDB, config/install, sqlfLogUpdateCfgParam,
  probe:20
  CHANGE : CFG DB WPROPDB2: "Maxappls" From: "126" <automatic> To:
  "175" <automatic>
  
  2019-03-06-09.07.45.854713 I41507A536 LEVEL: Event
  <snipped...>
  EDUID : 5678 EDUNAME: db2agent (SAMPLE) 3
  FUNCTION: DB2 UDB, config/install, sqlfLogUpdateCfgParam,
  probe:20
  CHANGE : CFG DB WPROPDB2: "Maxappls" From: "175" <automatic> To:
  "177" <automatic>
  
  2019-03-06-09.07.45.862132 I42044A536 LEVEL: Event
  <snipped...>
  EDUID : 9012 EDUNAME: db2agent (SAMPLE) 3
  FUNCTION: DB2 UDB, config/install, sqlfLogUpdateCfgParam,
  probe:20
  CHANGE : CFG DB WPROPDB2: "Maxappls" From: "177" <automatic> To:
  "178" <automatic>
  
  Note:
  The first db2diag.log message shown in description incorrectly
  indicates "file not found", but the error actually detected is
  "file sharing violation" in this case.
  Conflicts can occur on either Global or each member SQLDBCONF on
  purescale environment.
  

Local fix

• Avoid a situation where database configuration needs to be
  updated too frequently.
  Set MAXAPPLS to a fixed large number(e.g. 1000).
  For example
  db2 update db cfg for sample using MAXAPPLS 1000
  

Problem summary

• ****************************************************************
  * USERS AFFECTED:                                              *
  * all                                                          *
  ****************************************************************
  * PROBLEM DESCRIPTION:                                         *
  * See Error Description                                        *
  ****************************************************************
  * RECOMMENDATION:                                              *
  * Upgrade to Db2 11.1.4.6 or higher                            *
  ****************************************************************
  

Problem conclusion

• Upgrade to Db2 11.1.4.6 or higher
  

Temporary fix

Comments

APAR Information

• APAR is sysrouted FROM one or more of the following:

• APAR is sysrouted TO one or more of the following:

Fix information

• Fixed component name

  DB2 FOR LUW

• Fixed component ID

  DB2FORLUW

Applicable component levels

• RB10 PSN

     UP