Sometimes you are developing with kettle and you need to open several connections to the same database, in this case I will show how to check the amount of connections opened in Oracle. Below there are some useful queries:
-- Show sessions by user select osuser, username, machine, program from v$session order by osuser
-- Show sessions by application select program Application, count(program) Number_of_Sessions from v$session group by program order by Number_of_Sessions desc
If you detect you have too many connections it is time to convert your transformations transactional, using this feature you will prevent collapse the pool of connections. (Check the option Make the transformation database transactional? )
Below I attach a query to display the size and free space on the different tablespaces.
-- Show Tablespaces select b.tablespace_name, tbs_size SizeMb, a.free_space FreeMb from (select tablespace_name, round(sum(bytes)/1024/1024 ,2) as free_space from dba_free_space group by tablespace_name) a, (select tablespace_name, sum(bytes)/1024/1024 as tbs_size from dba_data_files group by tablespace_name) b where a.tablespace_name(+)=b.tablespace_name;