The Retrieve Lock Exclusive command allows you to determine if any
job has an *EXCL lock on an object. Certain display functions such
as DSPOBJAUT will fail if a *DTAARA object is locked by a different
job to *EXCL. DSPPFM will fail if a member is locked exclusively.
The API QWCLOGJL is used.
A typical series of commands would be:
DCL &JOB *CHAR LEN(10)
.
RTVLCKEXCL OBJ(ABC/XXX) OBJTYPE(*DTAARA)
JOB(&JOB)
IF ((%SST(&JOB 1 1) *NE '*') DO /* Not spcl */
/* */
/* Your handling of a different job */
/* has an *EXCL lock on the XXX */
/* data area in library ABC. */
/* */
ENDDO /* Not spcl */
IF ((%SST(&JOB 1 1) *EQ '*') DO /* Special */
/* */
/* Your handling of no job (other */
/* than possibly your own) has an */
/* *EXCL lock on the XXX data area */
/* in library ABC */
/* */
ENDDO /* Special */
When RTVLCKEXCL runs, it accesses any locks that are held on the
specified object. If an *EXCL lock is not found, the JOB return
variable will contain *NONE. If the current job holds an *EXCL lock,
the JOB return variable will contain *CURRENT (this is why the
typical coding shown checks for a special value).
Multiple locks
--------------
It is possible for a single job to hold multiple locks on the same
object such as *SHRRD and *EXCL or multiple *EXCL locks. In either
case, RTVLCKEXCL would return the job name because it holds at least
one *EXCL lock.
Only one job can hold an *EXCL lock on an object.
Data base locks
---------------
When ALCOBJ is used on a data base file such as:
ALCOBJ OBJ(ABC/XXX *FILE *EXCL)
A *SHRRD lock is placed on the file object. Even though the member
is not specified, there would be an *EXCL lock placed on the data of
the first member. It operates the same as if you had specified:
ALCOBJ OBJ(ABC/XXX *FILE *EXCL *FIRST)
Functions such as DSPOBJAUT may be used by any job on the file object
because they operate at the file level and not the member level.
Functions such as DSPPFM cannot be used by another job because of the
member lock.
There is no method of locking a data base file object to an *EXCL
level using ALCOBJ.
System locking for various functions
------------------------------------
The system places a lock on an object when a change is made such as
CHGDTAARA. These locks are normally held only for the duration of
the command and do not interfere with most other functions.
The ALCOBJ command does not have all the function that the locking
functions provided by the system. For example, you cannot allocate a
printer file type, but the system does for certain functions.
RTVLCKEXCL escape messages you can monitor for
----------------------------------------------
None. Escape messages from based on functions will be re-sent.
RTVLCKEXCL Command parameters *CMD
-----------------------------
OBJ The qualified name of the object to retrieve lock
information for.
The library value defaults to *LIBL. A specific library or *CURLIB
may also be used.
OBJTYPE The object type to retrieve lock information for.
Use the prompter for the supported values.
MBR The member name. The default is *NONE. A specific
member name or *FIRST may be entered.
If *NONE is specified for a data base file, the check is done for the
file object and not any of the members.
JOB The return variable for the job name which holds an
*EXCL lock. A variable name is required and must be
specified as *CHAR LEN(10).
If no job holds an *EXCL lock, *NONE is returned.
If the current job holds an *EXCL lock, *CURRENT is
returned.
USER The optional return variable for the user name of
the job which holds an *EXCL lock. If used, the
variable must must be specified as *CHAR LEN(10).
JOBNBR The optional return variable for the job number of
the job which holds an *EXCL lock. If used, the
variable must must be specified as *CHAR LEN(6).
QLFJOB The optional return variable for the qualified job
name which has *EXCL lock. This may be useful if
needed in a message. If used, the variable must
must be specified as *CHAR LEN(28).
Restrictions
------------
Because RTVLCKEXCL returns variables, the command may only be used in
a CL type of program.
Prerequisites
-------------
The following TAA Tools must be on your system:
CHKOBJ3 Check object 3
CRTUSRSPC Create user space
RSNLSTMSG Resend last message
SNDESCINF Send escape information
SNDESCMSG Send escape message
Implementation
--------------
None, the tool is ready to use.
Objects used by the tool
------------------------
Object Type Attribute Src member Src file
------ ---- --------- ---------- ----------
RTVLCKEXCL *CMD TAAOBMT QATTCMD
TAAOBMTC *PGM CLP TAAOBMTC QATTCL
TAAOBMTR *PGM RPG TAAOBMTR QATTRPG
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