estimate_only=y

will only give the size. It will not tell how many hours the export/import is going to take.

shrink datafiles

SQL>COLUMN SHRINK_DATAFILES FORMAT A75 WORD_WRAPPED
SQL>COLUMN VALUE NEW_VAL BLKSIZE
SQL>SELECT VALUE FROM V$PARAMETER WHERE NAME = 'DB_BLOCK_SIZE'
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SQL>SELECT 'ALTER DATABASE DATAFILE ''' FILE_NAME ''' RESIZE ' CEIL( (NVL(HWM,1)*&&BLKSIZE)/1024/1024 ) 'M;' SHRINK_DATAFILES FROM DBA_DATA_FILES DBADF,(SELECT FILE_ID, MAX(BLOCK_ID+BLOCKS-1) HWM FROM DBA_EXTENTS GROUP BY FILE_ID ) DBAFS WHERE DBADF.FILE_ID = DBAFS.FILE_ID(+) AND CEIL(BLOCKS*&&BLKSIZE/1024/1024)- CEIL((NVL(HWM,1)* &&BLKSIZE)/1024/1024 ) > 0
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drop temp tablespace in asm

DROP TABLESPACE TEMP INCLUDING CONTENTS AND DATAFILES
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add datafile to temp tablespace in asm

ALTER TABLESPACE TEMP ADD TEMPFILE '+DATA1_A3' SIZE 100M AUTOEXTEND ON NEXT 100M MAXSIZE UNLIMITED
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you can also specify user defined location instead of system generated one.

create temp tablespace in asm

CREATE TEMPORARY TABLESPACE TEMP TEMPFILE '+DATA1_A3' SIZE 100M AUTOEXTEND ON NEXT 100M MAXSIZE UNLIMITED EXTENT MANAGEMENT LOCAL UNIFORM SIZE 10M SEGMENT SPACE MANAGEMENT MANUAL
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dblink creation

make sure that you have the tnsentry of db2 in db1.

create public database link dblinkname connect to userindb2 identified by passwordindb2 using 'tnsentrynameindb2'
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verify
select * from dual@dblinkname
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you need to get x as the output.
select name from v$database@dblinkname
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you need to get db2name as the output.

you may get the error "ORA-02082: a loopback database link must have a connection qualifier" in case if you use the database link name as that of the global name in db2. To avoid this, you can either give a different database link name (or) you can change the global name, then create the database link and after that you change the global name back to its original name.

Query dba_db_links

reset the password

alter user username identified by password
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