How to resolve version tables in Netezza database?

whenever an alter happened on the Netezza table and NPS will make that table as version and collect the data from both version which is considered as costlier operation.

So we have to clear the  table versions periodically.

Versioned tables come about as a result of doing an

               ALTER TABLE <tablename> [ADD|DROP] COLUMN ...

          This results in multiple data stores for the table.  When you go to query

          the table, NPS must recombine the separate data stores back into a single

          entity.  This action will be performed automatically and on-the-fly.  But

          it does result in additional query overhead.  Therefore, it is a best

          practice to reconstitute the table as soon as practical by doing a

Here  is the script to find out the table versions in Netezza

/nz> nz_altered_tables 

# Of Versioned Tables         1                                        

     Total # Of Versions      2                                        

                                                                        

 Database |         Table Name         |       Size (Bytes)       | #  

Of Versions                                                            

----------+----------------------------+--------------------------+-----

----------                                                             

NZ_DB1 | TEST_TABLE_HISTORY |          197,591,957,504 |    

once you find the table ,then you need to clear the version using the below command.

 GROOM TABLE <tablename> VERSIONS;