SPEED and RECOVERY

richa.setia · New User Joined: 23 Mar 2005 Posts: 10 Location: Noida

Hi,

Can anyone please explain how do SPEED and RECOVERY work in VSAM?

Regards,
Richa

ideas · New User Joined: 25 May 2005 Posts: 52 Location: India

Richa,

{
When using the IDCAMS DEFINE command, there are two
mutually exclusive options that can be used. These are SPEED
and RECOVERY. RECOVERY is the default.

RECOVERY is only applicable when data is loaded into a
cluster for the first time - an activity known as initial load.
When RECOVERY is used, IDCAMS loads the data into a
cluster, and also preformats another Control Area with EOF
records. If the system crashes during this initial load, a
subsequent read of the file will identify how far the data load
had gone before the failure occurred. The load can then be
restarted from this point.

The alternative is to use SPEED. SPEED does no
preformatting of Control Areas with EOF records. Therefore
the initial load takes place faster, and fewer I/Os are
performed.

Apart from the overhead when using RECOVERY, it also
requires the user to work out where the initial load failure
occurred and to take all the necessary steps to restart the load
from the correct point. This may take a considerable amount
of time and require considerable effort on the part of the end
user.

In general, for all but the largest initial loads, it takes more
time to work out the restart logic than simply to rerun the
whole job again. Therefore, it is recommended that SPEED is
coded when performing the initial load for all but the largest
files.
}
In addition to this browse thru:http://documents.bmc.com/products/documents/09/25/20925/20925.pdf

jkbytes · Posted: Fri Jun 03, 2005 1:20 pm

In a nut shell,

Recovery:

REcovery the default, reformats the control areas during the initial dataset load so that we can restart the job if it abends for some reason.

Speed:

Speed indicates that the data was initially loaded with the speed parameter, which does not preformat the control areas when the data in initially loaded, and is faster than recovery, the default.