D Eloquence Library

The LOCK Function

   idb_lock(base,qual,mode,status)

   int base;
   void *qual;
   int mode;
   int status[10];

base

Identifies the database. This must be the return value from the idb_open call

qual

Identifies a data set, data item or lock qualifier, depending on the mode used. Refer to the description below for information on qualifier and Mode. Refer to the idb_find parameters dset and item for information on specifying the data set or data item.

mode

The modes available listed below.

status

A pointer to an array of at least 10 elements used to indicate the success or failure of the function call (see below).

Description

idb_lock modes

Mode	Target	Wait	Description
1	database	Write Wait	Lock database for writing
2	database	Write
3	data set	Write Wait	Lock data set for writing
4	data set	Write
5	predicate	Write Wait	Lock using for writing
6	predicate	Write	using predicate spec
11	database	Read Wait	Lock database for reading
12	database	Read
13	data set	Read Wait	Lock data set for reading
14	data set	Read
15	predicate	Read Wait	Lock for reading
16	predicate	Read	using predicate spec

A read lock allows concurrent read locks. A write lock does not allow any concurrent lock (it is a lock for WRITE).

A wait lock will block execution until lock is available. A lock without wait will return status error if lock is not available.

A lock with wait will fail and return status error if another lock has already been granted and the requested lock is not available.

The Lock Descriptor Format (next page) will explain how to set up predicate specification. Using predicate specification it is possible to lock database, data set(s) or (a group of) data item(s) to be locked.

Return value

Status codes

Status codes

Element	Meaning
0	S_OK
1	1
2	0
3	1
4	0
5	DB_LOCK | (open_mode << 12)
6	0
7	0
8	mode
9	0

Example

   if(idb_lock(dbid,"ORDER",4,status))
      error_handler();