SUMMARY d_keylock(FIELD,type[,dbn]) long FIELD; int dbn;
ARGUMENTS FIELD The field type of the key field for which is to be locked.
type Pointer to a string containing the type of lock to be applied.
dbn (optional) The number of the database containing the record.
DESCRIPTION Function d_keylock places a lock on the key file which contains occurrences of key field FIELD.The type of lock to be applied is specified by types as follows: Type Description "r" Read lock. "w" Write lock. "x" Exclusive lock. "k" Keep lock. Read lock allow other programs to read but not update the locked files. Write locks prevent all other programs from accesing the locked files and can only be issued from whithin transaction.Exckusive locks also prevent all other programs from accesing the locked files but not be issued independent of transactions.Keep locks can only be issued from within a transaction and will keep read- and write-locked files read-locked after a trasaction ends(d_trend normally frees all read- and write-locked files). The record type must be locked in order to apply a keep lock; otherwise status S_NOTLOCKED is returned.
Whithin a trasaction, a read-locked file can be upgraded to a write or exclusive lock by calling d_reclock with a write or exclusive lock where a read lock already exists.If the upgrate lock request is denied, the read lock will remain in effect.
This function is present in the single-user version of db_VISTA, but perfoms no action.This allows multi-user application to link whith the single user version for operation on stand-alone computer.
CURRENCY CHANGES None.
RETURN CODES
5 S_UNAVAIL The requested key file is not available(i.e. you weer on the queue waiting for the file longer than your current time out value). -5 S_INVFLD Invalid field type. -11 S_BADTYPE An invalid lock type was specified.You may have passed a character (e.g.'r') instead of a string (e.g."r") -17 S_NOTKEY FIELD is not defined as a key. -23 S_NOTFREE Key type alread locked by yuor application. -31 S_NOTRANS Requested a write lock outside of a transaction.
EXAMPLE /*display all info records in id_code order*/ while (d_keylock(ID_CODE,"r")==S_UNAVAIL) for(d_keylfrst(ID_CODE);db_status == S_OKAY; d_keypnext(ID_CODE)){ d_recread(&irec); .. /*print info record contens*/ }