VERIFY
[/?]
[ON]|[OFF]
/?The VERIFY command modifies the verify flag maintained by the operating system for the command interpreter process. If its argument is the single word "ON", it turns the verify flag on. If its argument is the single word "OFF", it turns the verify flag off. Any other argument is a syntax error. If no argument is supplied, VERIFY will write to its standard output text indicating whether the verify flag is currently on or off.
The verify flag is used by the operating system to perform "read-after-write verification". When this flag is on for a process, all writes to local disc media (by that process) are immediately followed by a read of the same sectors. (The data read are not compared with the data written. The only verification is that a read will succeed, not that it reads the same data that were written.) The extra I/O operations incurred for every disc write will cause a decrease in disc throughput.
The verify flag in a child process started by the command interpreter is inherited from the command interpreter process with the value that it had at that particular time. Any use of the VERIFY command in the command interpreter after a child process has been started will not affect that process.