It is one of the last resorting options available to DBA's when the system runs out of Cylinders.Packdisk helps to pack up cylinders in AMP making space for more data. We need to note that PACKDISK is an expensive operation on the system and it should be planned out so no parallel activities are run
Running PACKDISK on regular basis is part of Best Teradata practices. It also helps improve overall performance of the system .
How do you determine whether system is running out of space?
1. By using DBC.Diskspace ,
sum(currentperm)/1024/1024/1024 "cur_space_gb" ,
case when ((max_space_gb - cur_space_gb)/max_space_gb) *100 < 25
then 'Warning! Packdisk has to be run'
else 'No Packdisk activity required!' end
from DBC.Diskspace ;
2. By using Showspace from Ferret utility.
this would display free space per cylinder. When the free space is low,it would run minicylpacks which can impact the performance of system . So DBA's need to keep an eye on Free space per cylinder.
3. SHOWFSP another Ferret utility which is very useful in identifying particular tables that needs to packing.
It also shows amount of cylinders that can freed up by specifying Free space percent (FSP)
How to start PACKDISK?
please note that We can start /pause/ abort & continue packdisk whenever needed.
(type help to figure more options is you are not sure)
1. To start packdisk, go to ferret-> type PACKDISK
2. you can define range of FSP to start packdisk (say fsp =30 will start for cylinders having less than 30% free space)
3. Above option can be ignored and PACKDISK can be invoked for all cylinders)