When an application requires a table row, the program makes a call to TBLBASE. If this is the first access to the table, a data space will be allocated to accommodate the table. The table is loaded into a designated area in the data space called the tableSPACE Region (TSR), which is managed by tableBASE services. For a retrieval request, tableBASE searches the table according to its organization and search strategy, and returns the requested row to the application program.
The program needs only to provide a work space for one single row from the table. All accesses, updates, additions, and deletions are done in memory. Organization and search methods can also be modified dynamically (see Figure 69). The table remains in memory until the job terminates or a command is given to close the table, which clears it from memory and releases the space it occupies. Any number of applications may access one table for read access, however write access is limited.