Additional Space on Destination System | Teradata Vantage - Plan Additional Space on Destination System - Advanced SQL Engine - Teradata Database

Teradata recommends you have at least 20% free permspace available on the destination system. Additional permspace on the destination system may be required for the following reasons:

• Disabling BLC can cause space requirements to grow nearly 250% in extreme cases.
• Changing a table from NO FALLBACK to ALLWAYS FALLBACK will increase the space requirements by 100% for that table.
• New features and functionality add fields to existing system tables or may require new system tables.
• Table headers may increase in size.
• The new system may be configured with more AMPs. A copy of every table header is on every AMP.
• Hash function changes may result in data rows moving to different AMPs causing an out of space condition that did not exist previously.

  If the migration involves a hash function change, there must be enough free space in each database to hold an extra temporary copy of the largest table in that database. A hash function change may result in many rows being located on different AMPs on the destination system. When a row is redistributed to another AMP, the row is copied into a buffer to be sent to the new AMP. The space for the original copy of the row is not freed until the entire table has been restored and redistributed.

• The source and destination systems have different DBS Control settings. Some DBS Control settings, especially those related to block-level compression, affect space usage.

It is not only large databases that can run out of space. Use the following query on the source system to show the used and available space for each database:

SELECT DatabaseName,SUM(CurrentPerm), SUM(MaxPerm)
FROM DiskSpace GROUP BY 1
WITH SUM(CurrentPerm),SUM(maxperm) ORDER BY 1;

If SUM(CurrentPerm)/SUM(MaxPerm)>80%, the available free space on the system is below the recommended minimum threshold for migration.

Database USRP_32448 has exceeded it's logical space limit

SELECT SUM(DataBaseSpace.CurrentPermSpace)
(NAMED CurrentPerm, FORMAT '-,---,---,---,---,---,---,--9')                                                                               
FROM  DBC.Dbase, DBC.DataBaseSpace, DBC.TVM
WHERE DataBaseSpace.TableID <> '000000000000'XB
 AND  DataBaseSpace.TableID = TVM.tvmid
 AND  TVM.DatabaseId = Dbase.DatabaseId
 AND  TVM.TableKind NOT IN ('G','M','V')
 AND  TVM.ProtectionType = 'N';