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Articles on Trending Technologies
Technical articles with clear explanations and examples
Foreign key referencing of two DB2 tables
A foreign key is a column in a table that establishes a referential link with another table. A foreign key can be defined during creation of table (CREATE TABLE command) or it can be defined by modifying the table (ALTER TABLE command). However, before defining any key as foreign key, make sure that an index is built up on that column. We can use the below command to define an existing column CLASS in table TAB1 as a foriegn key which links to table TAB2.ALTER TABLE TAB1 ADD FOREIGN KEY (CLASS) REFERENCES CLASSDATA (CLASS_ID);The ALTER TABLE reserved words are followed ...
Read MoreHow to add a new column Address in the above DB2 table TAB1?
We can add a new column in an existing table as per the business requirements. Similarly, we can also remove a column from the table. This could be done using the ALTER table command as below.ALTER TABLE TAB1 ADD COLUMN ADDRESS VARCHAR(100);The ALTER TABLE reserved words are followed by the name of the table which we want to amend. In this case it is TAB1.To add a new column we will use ADD COLUMN and to remove the column we will use the REMOVE COLUMN parameter. This is followed by the name of the column. If this is an addition ...
Read MoreHow will you add a constraint on above DB2 table TAB1 for ages between 3 to 16 years?
Constraints are used to restrict the data inserted at a particular column. Constraints can be used in such a way that a value can only be inserted if it satisfies the condition given in constraints. We can give the below parameter during CREATE TABLE command to add a constraint.CREATE TABLE DBSET1.TAB1 (STUDENT_ID CHAR(10) NOT NULL, ENROLLMENT_ID CHAR(20) NOT NULL, NAME VARCHAR(50), AGE SMALLINT CONSTRAINT NUMBER CHECK (AGE >=3 AND AGE
Read MoreHow to add a unique index on the above table TAB1 for column Enrollment ID (ascending)?
An index is a lookup table that optimizes the searching of data. An index defined on any table can increase the query speed. The index can be built up on any column of the table and DB2 will generate a logical structure at backend. This will facilitate the search on the table using indexed columns effectively.An index can be unique and non-unique. To create a new unique index at any table we can use below command.CREATE UNIQUE INDEX ENROTAB1 ON TAB1 (ENROLLMENT_ID) ASC;The CREATE UNIQUE INDEX reserved words are followed by the name of the unique index which we ...
Read MoreHow to create a DB2 table TAB1 with 4 columns, Student ID, Enrollment ID, Name and Age?
A table is a logical structure of a data in a DB2. A table consists of a column which represents the attribute and rows represents the entity. Below command can be issued in order to create a new DB2 table.CREATE TABLE DBSET1.TAB1 (STUDENT_ID CHAR(10) NOT NULL, ENROLLMENT_ID CHAR(20) NOT NULL, NAME VARCHAR(50), AGE SMALLINT PRIMARY KEY (STUDENT_ID));The CREATE TABLE reserved words are followed by the name of the table which we have to create in the format . Here DBSET1 is the database and TAB1 is the table.The name of the column has to be ...
Read MoreHow to add volume VOL34 and remove volume VOL29 from storage group STG1?
A Volume is a group of physical disks which are used to store the data. A storage group is a collection of volumes. We can add or remove the volumes in a storage group in order to adjust the space. Below command can be issued in order to amend the volume in a storage group.ALTER STG1 ADD VOLUMES(VOL34) REMOVE VOLUMES(VOL29);The ALTER reserved word has to be followed by the name of the storage group which needs to be altered. Which is STG1 in this case. The ADD VOLUMES parameter has the list of volumes which needs to be ...
Read MoreHow to create a DB2 bufferpool with pagesize 4096?
Bufferpool is the unit of the main memory which is used to cache the data in the DB2 table. The data is stored in the cache once the database manager reads the data from the disk to the main memory. The bufferpool can be defined by giving the pagesize.The page is the smallest unit of Input/Output that a DB2 database manager can handle. We can create a DB2 bufferpool using the below command−CREATE BUFFERPOOL BP3 PAGESIZE 4096;The CREATE and BUFFERPOOL reserved words are followed by the bufferpool name which we want to create. Finally we will use PAGESIZE parameter to ...
Read MoreHow to create a DB2 storage group STG1 with volume VOL1.
Storage groups are basically the collection of volumes which hold the data that is present in the DB2 table. Basically it is the responsibility of DBA to maintain, add and update the storage groups in DB2.To create a storage group in a DB2 installation we have to give below command.CREATE STOGROUP STG1 VOLUMES (VOL1);The CREATE and STOGROUP are the reserved words which are followed by the name of the storage group. The volume parameter should be populated with the name of the volume for the storage group.
Read MoreHow to implement isolation levels CS, RR, UR and RS in a DB2 program?
The isolation level defines the degree to which the DB2 data which is being accessed in the COBOL-DB2 program is isolated with another parallelly executing COBOL- DB2 program. There are 4 main types of Isolation levels in DB2.Cursor stability (CS) - The cursor stability isolation level locks only the current row which the program is accessing. As soon as the program shifts to the next row, the lock in the previous row gets released. The cursor stability fetches only committed rows for the program to access. This is a default isolation level.Read stability (RS) - This isolation level places a ...
Read MoreImplementation of a table level locks in a COBOL-DB2 program during program execution
The COBOL-DB2 program can place the lock into a DB2 table in two ways.When the SQL statement using that table is executed within the program.When the program is loaded in the main memory and it is ready to be executed. It acquires a lock on all the DB2 tables which are used in the SQL statements within the program.To acquire the lock on all DB2 tables once the program is loaded in the main memory or allocated to a thread, we have to BIND the plan using appropriate options and parameters. Below is a JCL step which can be used.//BIND ...
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