The cyclic redundancy check (CRC) value for either an r-code file, or a database table corresponding to a buffer object.
When applied to the RCODE-INFO system handle, the r-code CRC is calculated during compilation and stored in the r-code file using the contents of the source files, including included files.
When applied to the
Buffer object handle, the database CRC is calculated using the metaschema _CRC field value from the _File record for the database record corresponding to the buffer object's table (which can be a standard or temp-table).
The CRC for a temp-table is calculated differently than for a standard table. Some differences include:
Standard tables have a _File record in the database that contains a _CRC field for the CRC value, which is calculated as you make changes to the table. Temp-tables do not have a _File record, and do not exist in a database.
The CRC values for both standard and temp-tables include the data type, extent and position of each column in the table, as well as index information. However, the CRC value for a standard table includes additional information that a CRC value for a temp-table does not (such as, the _Order field in the _File record).
The CRC value for a standard table is stored in a .r file. The AVM uses that CRC value at run time to verify the integrity of application r-code that uses the table. The AVM uses the CRC value for a temp-table to compare table parameters between a calling and called procedure (to avoid a field-by-field comparison).
