Tun SQL – Data Access - Esker

" RDBMSs and C-ISAMAs C-ISAM files use indexed sequential access, developers mustunderstand the file structure and use the index files to access data.Building a database system using C-ISAM files frees developers fromthese constraints by incorporating an indexed file structure as tables,columns, and indexes in a catalog." Tun SQL C-ISAMC-ISAM depends on C functions to query and update sequential files.The C-ISAM driver shipped with Tun SQL lets you view sequentialfiles as a standard relational database with tables, fields and keys. Youcan then use standard SQL instructions to query or update a databasecreated with C-ISAM files. The C-ISAM driver C-ISAM translates theinstructions into C functions that perform the necessary operations onthe sequential files.To go from a sequential data view to a relational database view, the C-ISAM driver adds descriptive database files known as the catalog to thestandard C-ISAM data and index files. These are C-ISAM type files(.dat data file and .idx index file): SysTables, SysColumns, SysIndexesand SysDefaults.SysTables SysColumns SysIndexes SysDefaultsfile1.datfile1.idxCatalog filessqltools is a UNIX tool for creating and managing databases built on C-ISAM. It works on the same principle: SQL instructions are used toconstruct the database and are translated into C functions before theycan be read by the C-ISAM file system.3 - 38 Data Access !