How to untar the file with tar.gz on AIX

ora@dba2a/HIST_ARCHIVE/bench>ls -l
total 3982944
-rw-r--r--    1 ora  staff    2039266987 Oct 04 09:50 dmp.tar.gz
ora@dba2a/HIST_ARCHIVE/bench>tar zxvf dmp.tar.gz
Usage: tar -{c|r|t|u|x} [ -BdDEFhilmopRUsvwZ ] [ -Number ] [ -f TarFil e ]
           [ -b Blocks ] [ -S [ Feet ] | [ Feet@Density ] | [ Blocksb ] ]
           [ -L InputList ] [-X ExcludeFile] [ -N Blocks ] [ -C Directory ] File ...
Usage: tar {c|r|t|u|x} [ bBdDEfFhilLXmNopRsSUvwZ[0-9] ] ]
           [ Blocks ] [ TarFile ] [ InputList ] [ ExcludeFile ]
           [ [ Feet ] | [ Feet@Density ] | [ Blocksb ] ] [-C Directory ] File ...
ora@dba2a/HIST_ARCHIVE/bench>tar -xvf dmp.tar.gz
tar: 0511-169 A directory checksum error on media; 0 not equal to 57571.

gunzip first and then untar the file

ora@dba2a/HIST_ARCHIVE/bench>gunzip dmp.tar.gz
ora@dba2a/HIST_ARCHIVE/bench>ls -l
total 4149328
-rw-r--r--    1 ora  oinstall 2124451840 Oct 04 09:50 dmp.tar
ora@dba2a/HIST_ARCHIVE/bench>tar xvf dmp.tar
x dmp
x dmp/expdp_ENCRYPT_MAPPING.log, 1126 bytes, 3 media blocks.
x dmp/expdp_lob_tabs.dmp, 664014848 bytes, 1296904 media blocks.
x dmp/expdp_ENCRYPT_MAPPING.dmp.gz, 534226647 bytes, 1043412 media blocks.
...