Apress.Expert.Oracle.Database.Architecture.9i.and.10g.Programming.Techniques.and.Solutions.Sep.2005

CHAPTER 3 ■ FILES 77
• To maintain a history of commented changes. In the past, many DBAs heavily commented
their parameter files with a change history. If they changed the size of the
buffer cache 20 times over the period of a year, for example, they would have 20 comments
in front of the db_cache_size init.ora parameter setting, stating the date and
reason for making the change. The SPFILE does not support this, but you can achieve
the same effect if you get into the habit of doing the following:
sys@ORA10G> create pfile='init_01_jan_2005_ora10g.ora' from spfile;
File created.
sys@ORA10G> !ls -l $ORACLE_HOME/dbs/init_*
-rw-rw-r-- 1 ora10g ora10g 871 Jan 1 17:04 init_01_jan_2005_ora10g.ora
sys@ORA10G> alter system set pga_aggregate_target=1024m
2 comment = 'changed 01-jan-2005 as per recommendation of George';
In this way, your history will be saved in the series of parameter files over time.
Fixing Corrupted SPFILEs
The last question that comes up with regard to SPFILEs is, “SPFILEs are binary files, so what
happens if one gets corrupted and the database won’t start? At least the init.ora file was just
text, so we could edit it and fix it.” Well, SPFILEs shouldn’t go corrupt any more than should a
data file, redo log file, control file, and so forth. However, in the event that one does, you have
a couple of options.
First, the amount of binary data in the SPFILE is very small. If you are on a UNIX platform,
a simple strings command will extract all of your settings:
[tkyte@localhost dbs]$ strings spfile$ORACLE_SID.ora
*.compatible='10.1.0.2.0'
*.control_files='/home/ora10g/oradata/ora10g/control01.ctl','/home/ora10g/oradata/or
a10g/control02.ctl','/home/ora10g/oradata/ora10g/control03.ctl'
...
*.user_dump_dest='/home/ora10g/admin/ora10g/udump'
On Windows, simply open the file with write.exe (WordPad). WordPad will display for you
all of the clear text in the file, and a simple cut and paste into init.ora will allow
you to create a PFILE you can use to start your instance.
In the event that the SPFILE has just “gone missing” (for whatever reason—not that I have
seen an SPFILE disappear), you can also resurrect the information for your parameter file
from the database’s alert log (more information on the alert log shortly). Every time you start
the database, the alert log will contain a section like this:
System parameters with non-default values:
processes = 150
timed_statistics = TRUE
shared_pool_size = 67108864
large_pool_size = 8388608
java_pool_size = 33554432
control_files
= C:\oracle\oradata\ora9ir2w\CONTROL01.CTL,