Sybase ASE fetching millions of rows is slow - sql

Question

A query on Sybase tables takes a long time to fetch when the returned row count is in the millions. Execution is fast with indexes, but fetch is slow. What are some ideas to improve the performance of the fetch?
The three tables are similar to:
CREATE TABLE Table1{ // data
commonCol1 varchar(50),
table1Col1 float,
table1Col2 varchar(50),
table1Col3 int default 0,
commonCol3 DATE,
PRIMARY KEY (commonCol1, commonCol3)
}
CREATE INDEX index1 ON Table1(commonCol1, table1Col1, table1Col2, table1Col3, commonCol3)
CREATE TABLE Table2{ // dep
commonCol2 varchar(50),
table2Col1 int default 0,
commonCol3 DATE,
PRIMARY KEY (commonCol2, commonCol3)
}
CREATE INDEX index2 ON Table2(commonCol2, table2Col1, commonCol3)
CREATE TABLE Table3 { // join
commonCol1 varchar(50),
commonCol2 varchar(50),
commonCol3 DATE,
PRIMARY KEY (commonCol1, commonCol2, commonCol3)
}
CREATE INDEX index3 ON Table3(commonCol1, commonCol2, commonCol3)
The query is:
CREATE PROCEDURE dbo.myProc #val1 varchar(50), #val2 varchar(50)
AS BEGIN
SELECT Table3.commonCol1, Table1.table1Col1, Table1.table1Col3 FROM Table3
INNER JOIN Table1 ON Table1.commonCol1 = Table3.commonCol1
INNER JOIN Table2 ON Table2.commonCol2 = Table3.commonCol2
WHERE Table1.table1Col2 = #val1 AND Table1.commonCol3 = CONVERT(DATE, #val2) AND Table2.commonCol3 = CONVERT(DATE, #val2) AND Table3.commonCol3 = CONVERT(DATE, #val2)
GROUP BY Table3.commonCol1, Table1.table1Col1, Table1.table1Col3
HAVING MIN( Table2.table2Col1 ) = 1 AND ( MAX( Table1.table1Col3 ) <=1 OR MIN( ABS ( ROUND( Table1.table1Col1, 4) ) ) > 0 )
END