Execution Steps of DBMS – Sequence of events When DBMS Reads A Record –

Execution Steps of DBMS –

The events that occur when an application program reads a record by means of DBMS is shown in fig.

  1. Application Program A issues a request to the DBMS to read a record.
  2. The DBMS obtains the subschema and look up the description of the data in question.
  3. The DBMS obtains the schema and determines which logical data types are needed.
  4. The DBMS contains the  physical data base description  and determines which physical record(s) to be read.
  5. A command is issued by the DBMS to the operating system to read the required record(s).
  6. The operating system interacts which the physical storage where the data are kept.
  7. The required data are transferred  between the storage an the system buffers.
  8. Comparing the  schema and the subschema,  the DBMS derives from the data, the logical record needed by the application program.
  9. The data is transferred by the DBMS from the system buffers to the  program work area.
  10. The status information is given by the DBMS  to the application program, included any error indication.
  11. The application program then operates with the data in a work area.

Execution Steps of DBMS -Sequence of events When DBMS Reads A Record


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