select current_size from v$sga_dynamic_components where component = 'streams pool';

/* Streams pool advice */
COLUMN STREAMS_POOL_SIZE_FOR_ESTIMATE  HEADING 'Streams Pool|Size for Estimate'
  FORMAT 999999999999
COLUMN STREAMS_POOL_SIZE_FACTOR HEADING 'Streams Pool|Size|Factor' FORMAT 99.9
COLUMN ESTD_SPILL_COUNT HEADING 'Estimated|Spill|Count' FORMAT 99999999
COLUMN ESTD_SPILL_TIME HEADING 'Estimated|Spill|Time' FORMAT 99999999.99
COLUMN ESTD_UNSPILL_COUNT HEADING 'Estimated|Unspill|Count' FORMAT 99999999
COLUMN ESTD_UNSPILL_TIME HEADING 'Estimated|Unspill|Time' FORMAT 99999999.99
 
SELECT STREAMS_POOL_SIZE_FOR_ESTIMATE,
       STREAMS_POOL_SIZE_FACTOR, 
       ESTD_SPILL_COUNT, 
       ESTD_SPILL_TIME, 
       ESTD_UNSPILL_COUNT,
       ESTD_UNSPILL_TIME
  FROM V$STREAMS_POOL_ADVICE;