How applications access data

Application programs can access data in three ways: update, read, or read-only access.

You indicate the type of access on the PROCOPT keyword as part of the group of statements that comprise the program communication block (PCB) for a particular database access. These processing options for an application program are declared in the program specification block (PSB) and express the data access and alteration intent of the application program.

If an application program is to insert, delete, replace, or perform a combination of these actions, the application program has update access, which is specified with the PROCOPT=A keyword. An online application program that has exclusive access is also interpreted as having update access; update access is specified with the PROCOPT=E keyword.

Application programs that need access to a database but do not update the data can do so in two ways. They can access the data with the assurance that any pending changes have been committed by the application program that initiated the change. This type of access is read access and is specified with the PROCOPT=G keyword. Alternatively, application programs can read uncommitted data, if the application program does not specify protection of data status. This type of access is read-only access and is specified with the PROCOPT=GO keyword.

For more information on PROCOPT keyword values, see IMS Version 15 Application Programming.