DB2 9.5 - Shrink Tablespace

I'm trying to run the following: db2 alter tablespace TABLESPACE1 reduce I keep getting errors. As you can see, I have around 50% free pages. I'd like to shrink it in order to reclaim OS disk space. Tablespace ID = 281 Name = TABLESPACE1 Type = Database managed space Contents = All permanent data. Large table space. State = 0x0000 Detailed explanation: Normal Total pages = 8943720 Useable pages = 8943696 Used pages = 4559696 Free pages = 4384000 High water mark (pages) = 8914736 Page size (bytes) = 32768 Extent size (pages) = 8 Prefetch size (pages) = 24 Number of containers = 3 Minimum recovery time = 2014-12-09-16.28.18.000000 Container ID = 0 Name = /data/db2dat_10/sida1/TABLESPACE1_01.dbf Type = File Total pages = 2981240 Useable pages = 2981232 Accessible = Yes Container ID = 1 Name = /data/db2dat_11/sida1/TABLESPACE1_02.dbf Type = File Total pages = 2981240 Useable pages = 2981232 Accessible = Yes Container ID = 2 Name = /data/db2dat_12/sida1/TABLESPACE1_03.dbf Type = File Total pages = 2981240 Useable pages = 2981232 Accessible = Yes