Perform the select below to know the size all tables in a specific schema:

db2 "select substr(a.tabname,1,30), (a.fpages*PAGESIZE/1024) as size_k, a.card from syscat.tables a, \
syscat.tablespaces b where a.TBSPACEID=b.TBSPACEID and a.tabschema='<schema_name>"

DB29.1 or later:

db2 "SELECT tabname,TABSCHEMA, SUM(DATA_OBJECT_P_SIZE)+
SUM(INDEX_OBJECT_P_SIZE)+ SUM(LONG_OBJECT_P_SIZE)+
SUM(LOB_OBJECT_P_SIZE)+ SUM(XML_OBJECT_P_SIZE) FROM
SYSIBMADM.ADMINTABINFO where TABSCHEMA=<tabschema_name> group by tabname,tabschema" 

Perform the select below to know the size one table:

db2 "select substr(a.tabname,1,30), (a.fpages*PAGESIZE/1024) as size_k,
a.card from syscat.tables a, syscat.tablespaces b where
a.TBSPACEID=b.TBSPACEID and a.tabname='<tab_name>'  and tabschema='<schema_name>' "

DB29.1 or later:

 db2 "SELECT TABSCHEMA, TABNAME, SUM(DATA_OBJECT_P_SIZE)+
SUM(INDEX_OBJECT_P_SIZE)+ SUM(LONG_OBJECT_P_SIZE)+
SUM(LOB_OBJECT_P_SIZE)+ SUM(XML_OBJECT_P_SIZE) FROM
SYSIBMADM.ADMINTABINFO where tabschema='<tabschema_name>' and tabname='<table_name>' group by tabschema,tabname" 

Perform the select below to know the size of all schema:

db2 "select sum(a.fpages*PAGESIZE/1024) as size_k_of_schemaName  from syscat.tables a, \ 
syscat.tablespaces b where a.TBSPACEID=b.TBSPACEID and a.tabschema='<schema_name>' group by a.tabschema"

 DB29.1 or later:

 db2 "SELECT TABSCHEMA, SUM(DATA_OBJECT_P_SIZE)+
SUM(INDEX_OBJECT_P_SIZE)+ SUM(LONG_OBJECT_P_SIZE)+
SUM(LOB_OBJECT_P_SIZE)+ SUM(XML_OBJECT_P_SIZE) FROM
SYSIBMADM.ADMINTABINFO GROUP BY TABSCHEMA" 

Do you know the diference between FPAGES AND NPAGES ???

NPAGES - Total number of pages on which the rows of the table exist
FPAGES - Total number of pages

So, FPAGES >= NPAGES, when you run the utilities reorg and runstats, the reorg will try to do FPAGES=NPAGES and the runstats will update the statistics on catalog.