ALTER SYSTEM/DATABASE acts upon?

Question

Hi,
I have a question inside my head since a long time now, I did lot of googling, but did'nt find a precise answer.
All DMLs will be served by Dedicated/Shared server processes as per the configuration. Selects/Updates/Deletes/Inserts will have their execution plans generated to/used from the Library Cache of shared pool; will have their corresponding buffers put into the RLB and from there into redo log files. This is found every where on the web.
But what happens when we issue an "ALTER SYSTEM ... ... ..." or an "ALTER DATABASE ... ... ..."?
Does the user process adjust the SGA_TARGET/PGA_AGGREGATE_TARGET or it just signals MMAN?
Does it Flush Buffer Cache/Shared Pool or does it just signal the MMAN again? What happens inside?
Does it kill the sessions itself or just signal the PMON?
Which process starts up first and takes on when "STARTUP;" is issued?
Which process gears up to Close, Dismount, and Shut down the database stagewise in the mode requested by "SHUTDOWN ....;"?
Any link that discusses these and other such internal Oracle algorithms/implementations would be greatly helpful.
Thanks,
Aswin.

Answer 1

Hi,
ice_cold_aswin wrote:
Does it kill the sessions itself or just signal the PMON?
Which process starts up first and takes on when "STARTUP;" is issued?
Which process gears up to Close, Dismount, and Shut down the database stagewise in the mode requested by "SHUTDOWN ....;"?I think at least these can be answered by using strace. For example, starting up an instance:
[oracle@localhost ~]$ strace -o trc.txt -f -t -e trace=process sqlplus / as sysdba
SQL*Plus: Release 11.2.0.1.0 Production on Tue Mar 30 00:20:49 2010
Copyright (c) 1982, 2009, Oracle.  All rights reserved.
Connected to an idle instance.
SQL> startup
ORACLE instance started.
Total System Global Area            535662592 bytes
Fixed Size                            1337720 bytes
Variable Size                       335545992 bytes
Database Buffers                    192937984 bytes
Redo Buffers                          5840896 bytes
Database mounted.
Database opened.
18924 00:20:49 execve("/u01/app/oracle/product/11.2.0/dbhome_1/bin/sqlplus", ["sqlplus", "/", "as", "sysdba"], [/* 40 vars */]) = 0
18924 00:20:49 clone(child_stack=0, flags=CLONE_CHILD_CLEARTID|CLONE_CHILD_SETTID|SIGCHLD, child_tidptr=0xb7f81708) = 18925
18925 00:20:49 execve("/u01/app/oracle/product/11.2.0/dbhome_1/bin/oracle", ["oracletest11g2", "(DESCRIPTION=(LOCAL=YES)(ADDRESS"], [/* 41 vars */]) = 0
18925 00:20:51 clone(child_stack=0, flags=CLONE_CHILD_CLEARTID|CLONE_CHILD_SETTID|SIGCHLD, child_tidptr=0xae2708) = 18926
18926 00:20:51 execve("/bin/sh", ["/bin/sh", "-c", "/bin/df -k /u01/app/oracle/produ"], [/* 42 vars */]) = 0
18926 00:20:51 execve("/bin/df", ["/bin/df", "-k", "/u01/app/oracle/product/11.2.0/d"], [/* 42 vars */]) = 0
18926 00:20:51 exit_group(0)            = ?
18925 00:20:51 waitpid(18926, NULL, 0)  = 18926
18925 00:20:51 --- SIGCHLD (Child exited) @ 0 (0) ---
18925 00:20:52 clone(child_stack=0, flags=CLONE_CHILD_CLEARTID|CLONE_CHILD_SETTID|SIGCHLD, child_tidptr=0xae2708) = 18927
18927 00:20:52 clone(child_stack=0, flags=CLONE_CHILD_CLEARTID|CLONE_CHILD_SETTID|SIGCHLD, child_tidptr=0xae2708) = 18928
18927 00:20:52 exit_group(0)            = ?
18925 00:20:52 --- SIGCHLD (Child exited) @ 0 (0) ---
18925 00:20:52 waitpid(18927, [{WIFEXITED(s) && WEXITSTATUS(s) == 0}], 0) = 18927
18928 00:20:52 execve("/u01/app/oracle/product/11.2.0/dbhome_1/bin/oracle", ["ora_pmon_test11g2"], [/* 46 vars */]) = 0
18925 00:20:52 clone(child_stack=0, flags=CLONE_CHILD_CLEARTID|CLONE_CHILD_SETTID|SIGCHLD, child_tidptr=0xae2708) = 18929
18929 00:20:52 clone(child_stack=0, flags=CLONE_CHILD_CLEARTID|CLONE_CHILD_SETTID|SIGCHLD, child_tidptr=0xae2708) = 18930
18929 00:20:52 exit_group(0)            = ?
18925 00:20:52 --- SIGCHLD (Child exited) @ 0 (0) ---
18925 00:20:52 waitpid(18929, [{WIFEXITED(s) && WEXITSTATUS(s) == 0}], 0) = 18929
18930 00:20:52 execve("/u01/app/oracle/product/11.2.0/dbhome_1/bin/oracle", ["ora_vktm_test11g2"], [/* 46 vars */]) = 0
18930 00:20:52 clone(child_stack=0, flags=CLONE_CHILD_CLEARTID|CLONE_CHILD_SETTID|SIGCHLD, child_tidptr=0x4b3708) = 18931
...