Technical Blog Post
Abstract
75 ways to demystify DB2 #46: Techtip : What Happens at DB2 Instance Startup?
Body
When troubleshooting db2start related issues, we often hear this question - what exactly happens at DB2 instance startup?
db2start
- User command to start the db2 instance
- Checks for authorization by forking/exec db2chkau
- Checks for existence of db2nodes.cfg file
- Forks/exec db2star2 and waits for completion
db2star2
- Actual start process
- Checks authorization
- Creates the DBMS Memory set
- Checks licenses
- Forks/exec db2sysc and waits for completion
db2sysc – DB2 system controller
- Connects to the Instance shared memory already allocated
- Forks a db2sysc
- Renames the process to db2wdog
- Watchdog monitors the db2sysc process for abnormal termination
System controller process – db2sysc
- Starts db2gds (generic daemon spawner) to handle EDU creation
If DB2COMM is set,
> Start appropriate communication listeners
- db2ipccm, for local client connections
- db2tcpcm, for TCP/IP connections
- db2tcpdm, for TCP/IP discovery tool requests
Then an entry is written to the db2diag.log indicating successful start operation
[{"Business Unit":{"code":"BU058","label":"IBM Infrastructure w\/TPS"},"Product":{"code":"SSEPGG","label":"Db2 for Linux, UNIX and Windows"},"Component":"","Platform":[{"code":"PF025","label":"Platform Independent"}],"Version":"","Edition":"","Line of Business":{"code":"LOB10","label":"Data and AI"}}]
UID
ibm11141012