Keeping Your Informix rootdbs Lean and Clean (cont.)
Confirming the Contents of rootdbs
When you see a rootdbs larger than 50–75MB, you can be pretty sure that the logical and physical log files have been left in the rootdbs. The only database objects that need to be in the rootdbs are the system tables and other internal data structures that are managed by IDS.
You can confirm the contents of your rootdbs by running the following command:
oncheck –pe > tempfile
The only database objects that you should find in chunk 1 (the rootdbs) are the following:
Objects in the sysmaster database
Objects in the sysutils database
TABLESPACE TABLESPACE
ROOT DBspace RESERVED Pages
CHUNK FREE LIST PAGE
DATABASE TABLESPACE
FREE space (chunk space that is not currently allocated to tables)
If you have found physical or logical log files in the rootdbs or if you have found other database objects, you should consider moving them out of the rootdbs to improve performance and maintainability.
Choosing the Right Disk Spaces for Log Files
One factor affecting performance is access speed. The high write loads that are placed on the logical and physical log files means there is an excessive disk head movement as the head tries to read from many non-adjacent areas of the disk. To avoid this disk thrashing, you should place the logical and physical log files only on your fastest-writing disk spaces.
It's best not to put them in RAID 5 spaces because write speeds are slower on RAID 5 systems. Instead, place them either on individual disks or mirrored disks.
Placing the logical and physical log files in the rootdbs can cause severe performance and maintenance issues if not dealt with early on.
Confirm the contents of rootdbs, choose the right disk spaces for the log files, place the logical and physical logs in their own dbspaces, and decide where to place user databases.
Whose responsibility is it to make sure that configuration errors do not happen? Should the designer handle these issues or should it be left to the onside DBA? Discuss it in the informix.general discussion group!
