slow performance on Siebel CRM system

We experience very slow performance on CRM system currently. We find system is suspened by below SQL, I think this is sql execution when user login system. Is it possbile to enhance the system performance?

SELECT T10.CONFLICT_ID, T10.LAST_UPD, T10.CREATED, T10.LAST_UPD_BY, T10.CREATED_BY, T10.MODIFICATION_NUM, T10.ROW_ID, T10.ABSTRACT, T10.ACTIVATE_DT, T10.UNIVERSAL_MSG_FLG, T10.DISA_DISMISS_FLG, T10.MSG_BODY, T10.EXPIRATION_DT, T10.BRDCST_MSG_ID, T10.PRDINT_ID, T10.PR_RECIP_ORG_ID, T10.PR_RECIP_POSTN_ID, T10.PR_RECIP_USER_ID, T1.NAME, T10.BCST_MSG_TYPE_CD, T9.STATUS_VAL, T10.BRDCST_VIA_MB_FLG, T5.NAME, T7.ROW_ID, T2.LOGIN, T8.NAME, T6.ROW_ID, T3.LOGIN, T4.ROW_ID, T7.ROW_ID, T6.ROW_ID, T4.ROW_ID, :1 FROM SIEBEL.S_PROD_INT T1, SIEBEL.S_USER T2, SIEBEL.S_USER T3, SIEBEL.S_PARTY T4, SIEBEL.S_POSTN T5, SIEBEL.S_PARTY T6, SIEBEL.S_PARTY T7, SIEBEL.S_ORG_EXT T8, SIEBEL.S_BCSTMSG_USER T9, SIEBEL.S_BRDCST_MSG T10 WHERE T10.ROW_ID = T9.MSG_ID (+) AND T9.USER_ID (+) = :2 AND T10.PRDINT_ID = T1.ROW_ID (+) AND T10.PR_RECIP_POSTN_ID = T7.ROW_ID (+) AND T10.PR_RECIP_POSTN_ID = T5.PAR_ROW_ID (+) AND T5.PR_EMP_ID = T2.PAR_ROW_ID (+) AND T10.PR_RECIP_ORG_ID = T6.ROW_ID (+) AND T10.PR_RECIP_ORG_ID = T8.PAR_ROW_ID (+) AND T10.PR_RECIP_USER_ID = T4.ROW_ID (+)