What are Edge Nodes or Gateway Nodes in Hadoop?

Edge nodes are the interface between the Hadoop cluster and the outside network from which Hadoop user can store files in Hadoop cluster. It’s a gateway to the cluster, Hence some time we refer it as a gateway node as well.

Commonly, edge nodes are used to run cluster administration tools and client applications.  Edge-nodes are kept separate from the cluster nodes that contain HDFS, MapReduce, etc components in it, It mainly to keeps the computing resources separate from the outer world.

Edge nodes running within the cluster allow for centralized management of all the Hadoop configurations on the cluster nodes which helps to reduce the administration efforts needed to update the config files through cluster administrators. 

It’s a limited security within Hadoop itself, even if your Hadoop cluster operates in a LAN or WAN behind a security firewall. You may consider a cluster-specific firewall to fully protect non-public data of Hadoop cluster.

How to change a non-partitioned table into a partitioned table in oracle along with indexes?

There are two ways to change the partitioned table into non-partitioned table.

1. We can use Oracle data pump (expdp/impdp) utilities with option PARTITION_OPTIONS=DEPARTITION.

CREATE OR REPLACE DIRECTORY TEST_DIR AS '/oracle/expimpdp/';
GRANT READ, WRITE ON DIRECTORY TEST_DIR TO MY_USER;

EXPDP MY_USER/MY_PWD@MYDB TABLES=T DIRECTORY=TEST_DIR PARALLEL=5 INCLUDE=TABLE_DATA,INDEX COMPRESSION=ALL DUMPFILE=T_DUMP.DMP LOGFILE=EXPDP_T_DUMP.LOG

IMPDP MY_USER/MY_PWD@MYDB tables=T DIRECTORY=TEST_DIR PARALLEL=5 INCLUDE=TABLE_DATA,INDEX CONTENT=ALL PARTITION_OPTIONS=DEPARTITION DUMPFILE=T_DUMP.DMP LOGFILE=IMPDP_T_DUMP.LOG

2.  we can use ALTER TABLE - "ONLINE" & optional "UPDATE INDEXES"  Clause as below.

ALTER TABLE EMP_PART_CONVERT MODIFY PARTITION BY RANGE (employee_id) INTERVAL (100) 
( 
PARTITION P1 VALUES LESS THAN (100), 
PARTITION P2 VALUES LESS THAN (500) ) 
ONLINE UPDATE INDEXES 
(
IDX1_SALARY LOCAL, 
IDX2_EMP_ID GLOBAL PARTITION BY RANGE (employee_id) ( PARTITION IP1 VALUES LESS THAN (MAXVALUE)
)
);

Please note following things  - When using the UPDATE INDEXES clause:

• This clause can be used to change the partitioning state of indexes and storage properties of the indexes being converted.
• Indexes are maintained both for the online and offline conversion to a partitioned table.
• This clause cannot change the columns on which the original list of indexes are defined.
• This clause cannot change the uniqueness property of the index.
• This conversion operation cannot be performed if there are domain indexes.
• During conversion - All Bitmap indexes become local partitioned indexes, by default.