HP 3000 Manuals HP 3000 Manuals
MUSTRECOVER for Logged Databases by Mark Boronkay Commercial Systems Division/DBL Although TurboIMAGE provides database logging and recovery, it does not require that these options be used. If the database administrator chooses not to recover the database after a system failure or halt, it is possible that the database may remain in a logically inconsistent state. Because of this, database administrators have requested a way of preventing users from modifying a database until a proper recovery is done. The MUSTRECOVER option allows the database administrator to specify that a given database must be recovered after a system failure before it can be used. For a detailed description of how MUSTRECOVER works please refer to the related article in the "Technical Articles" section in this Communicator. EXPLANATION OF MUSTRECOVER The first writer in a database enabled for MUSTRECOVER causes TurboIMAGE to set an internal flag during DBOPEN. The flag is reset by the last writer during DBCLOSE. When on, this flag informs TurboIMAGE that some kind of data modification intrinsic (i.e., DBPUT, DBDELETE or DBUPDATE) may have been called. If the system fails after DBOPEN has set this internal flag, but before DBCLOSE has reset it, the flag will remain on after the system is restarted. Subsequent DBOPENs by writers will fail and will return a condition code of -34 in the first word of the status array. This condition code signifies that the database must be recovered before it can be DBOPENed successfully by a writer.
NOTE The database administrator can override this error and allow database access without proper recovery by disabling MUSTRECOVER (see Disabling MUSTRECOVER example #3 in the related article in the "Technical Articles" section).