Opens a database root file and maps its global section to the
contents of an OpenVMS virtual address file. You can use the RMU
Open command in conjunction with the SQL ALTER DATABASE statement
to control access to the database. See the description of the
OPEN IS {AUTOMATIC | MANUAL} clause of the SQL ALTER DATABASE
statement in the Oracle Rdb SQL Reference Manual for details.
1 – Description
Once you use the RMU Open command to open a database, the
database remains open and mapped until you close it explicitly
with an RMU Close command and all users have exited the database
with the SQL DISCONNECT or EXIT statements. If you do not issue
the RMU Open command, the first user to attach to the database
incurs the cost of implicitly opening it and the last user to
detach from the database incurs the cost of implicitly closing
it.
The effect of the RMU Open command depends on whether you have
specified the OPEN IS AUTOMATIC or OPEN IS MANUAL clause to the
SQL ALTER DATABASE statement, as follows:
o OPEN IS AUTOMATIC
If you have specified automatic opening for your database,
users can invoke the database at any time without first
issuing an RMU Open command. (Although as mentioned above,
it is more efficient to explicitly open the database with an
RMU Open command and close it with an RMU Close command.)
o OPEN IS MANUAL
If you have specified manual opening for your database, the
RMU Open command must be issued before users can invoke the
database.
If you modify the database attribute from OPEN IS AUTOMATIC
to OPEN IS MANUAL, the modification takes effect only after
all users have detached from the database. (You can issue the
RMU/CLOSE/ABORT=FORCEX command to force all users to detach.)
Then, you must issue the RMU Open command before users can invoke
the database.
If you modify the database attribute from OPEN IS MANUAL to OPEN
IS AUTOMATIC, users can invoke the database at their discretion.
You do not have to issue the RMU Open command. However, if a
user has already opened the database manually when you make this
change to the database attribute, the modification takes effect
only after you manually close the database by issuing the RMU
Close command.
See the Oracle Rdb Guide to Database Maintenance for information
to help you decide whether to set your database attribute to
automatic or manual opening.
When you create a database, you have a choice of how to set up
buffers for database pages. You can choose either local or global
buffering. Global buffers can provide better system performance.
See the Oracle Rdb7 Guide to Database Performance and Tuning for
more information on setting the number of global buffers for your
system.
2 – Format
(B)0[m [4mCommand[m [4mQualifiers[m x [4mDefault[m
x
/Access=[Un]Restricted x See description
/Global_Buffers[=(Total=i,User_Limit=j)] x See description
/Path x None
/Row_Cache=Disable x See description
/[No]Statistics=Import x /Nostatistics
/[No]Wait x /Nowait
3 – Parameters
3.1 – root-file-spec
root-file-spec[,...]
Specifies the database to open. If the database root file is
open, you receive an informational message. The default file
extension is .rdb.
4 – Command Qualifiers
4.1 – Access
Access=Restricted
Access=Unrestricted
Permits the database administrator to open the database
and restrict access to it in order to perform maintenance
operations or to restructure the database without interference
from users who want to gain access. If access is restricted
(Access=Restricted), the DBADM privilege is required for SQL
access to the database. If the Access=Unrestricted qualifier is
specified, users without the DBADM privilege can attach to the
database.
NOTE
Do not confuse the Oracle RMU Access=Restricted qualifier
with the SQL restricted access clause (available for use
with the following SQL statements: ATTACH, CREATE, DECLARE
ALIAS, and IMPORT). When you specify the restricted access
clause in SQL, only one user can attach to the database;
when you specify the Access=Restricted qualifier using
Oracle RMU, any number of users with the DBADM privilege
can access the database.
Furthermore, note that an SQL SHOW DATABASE command
displays the phrase "No Restricted Access" or the phrase
"Restricted Access" if access has been restricted using the
SQL restricted access clause. However, SHOW DATABASE tells
you nothing about whether Oracle RMU has opened a database
with access restricted. Use the RMU Dump command to view the
Oracle RMU access setting.
Refer to the Oracle Rdb SQL Reference Manual for more
information on the SQL restricted access clause.
If you specify the RMU Open command without the Access qualifier,
Oracle RMU opens the database in the same access mode as the last
RMU Open command performed. If the database was last opened as
restricted, issuing the RMU Dump command results in the following
message being displayed:
Access restricted to privileged users
Use this form of the RMU Open command to open the database on
other nodes without changing the access mode.
The access mode is clusterwide and the last mode set with the RMU
Open command is used for the entire cluster.
For example, if you open the mf_personnel database on node A with
the Access=Unrestricted qualifier, and open the same database
on node B with the Access=Restricted qualifier, the database
has restricted access on both node A and node B. However, the
commands do not terminate any user processes that may have gained
access while the database was unrestricted.
The access mode is stored in the database. Consequently, if
the system fails while access is restricted, access remains
restricted unless the unrestricted mode is explicitly requested.
The RMU Backup, RMU Restore, and RMU Copy_Database commands also
preserve the access mode.
The RMU Close command does not alter the access mode. You can
change the mode by using the RMU Open command only. You can use
the RMU Open command to restrict access to any database, whether
it was opened as AUTOMATIC or MANUAL.
The Access qualifier is a positional qualifier.
4.2 – Global Buffers
Global_Buffers[=(Total=i,User_Limit=j)]
Allows you to set the basic global buffer parameters on each
RMU Open command. If you specify the Global_Buffers qualifier,
you can optionally specify values for the Total and User_Limit
parameters:
o Total is the number of global buffers per node to allocate for
this opened instance of the database (minimum = 5, and maximum
o User_Limit is the maximum number of global buffers to be
allotted to any given user (minimum = 5, maximum = Total).
The default values for Total and User_Limit are set by:
o The RMU Open command explicitly
o Values determined at the time the database was created
If you do not specify a value for the Total or User_Limit
options, the values are determined based on what they were when
the database was created.
If a database does not have global buffers enabled, the Global_
Buffers qualifier is ignored. Use the RMU Dump command to see
if global buffering is enabled or disabled. The RMU Dump command
also shows the global buffer count and the maximum global buffer
count per user. For example:
$ RMU/DUMP MF_PERSONNEL
*------------------------------------------------------------------
* Oracle Rdb V7.0-00 22-SEP-1995 10:11:51.14
*
* Dump of Database header
* Database: DISK1:[DATABASE]MF_PERSONNEL.RDB;1
*
*-------------------------------------------------------------------
Database Parameters:
Root filename is "DISK1:[DATABASE]MF_PERSONNEL.RDB;1"
Created at 7-APR-1994 16:50:09.01
Oracle Rdb structure level is 70.0
Maximum user count is 50
Maximum node count is 16
Database open mode is AUTOMATIC
Database close mode is AUTOMATIC
Database is available for READ WRITE access
Snapshot mode is NON-DEFERRED
Statistics are enabled
Storage Areas...
- Active storage area count is 10
- Reserved storage area count is 0
Buffers...
- Default user buffer count is 20
- Default recovery buffer count is 20
- Global buffers are enabled <--------
- Global buffer count is 250 <--------
- Maximum global buffer count per user is 5 <--------
- Buffer size is 6 blocks
.
.
.
Derived Data...
- Global section size
With global buffers disabled is 70962 bytes
With global buffers enabled is 975992 bytes
.
.
.
The Global_Buffers qualifier is a positional qualifier.
4.3 – Path
Path
Specifies the full or relative data dictionary path name in which
the definitions reside for the database you want to open.
The Path qualifier is a positional qualifier. The path name
cannot include wildcard characters.
4.4 – Row Cache=Disable
Disables row caching. This qualifier is provided for use with hot
standby databases. Row caching cannot be enabled on a hot standby
database while replication is active. If it is enabled, the hot
standby feature will not start.
4.5 – Statistics=Import
Statistics=Import
Nostatistics
Specifies that statistic information previously saved by using
the Statistics=Export qualifier on the RMU Close command is to be
loaded when the database is opened. The default is Nostatistics,
which indicates that statistic information is not loaded when the
database is opened.
After the database is opened using the Statistics=Import
qualifier, the saved statistics file is closed. The statistics
file is not automatically deleted. It can be deleted if it is no
longer needed.
When you use the Statistics=Import qualifier, statistics
information is automatically preserved in the event of abnormal
database closure. To ensure that the ondisk statistic information
files are accurate in the case of a node or monitor failure,
the statistic information files are checkpointed by the database
monitor every half-hour. The RMU Show Users command identifies
when the checkpoint for each database occurs.
The statistic files are not loaded if the physical schema of the
database has changed since the statistic file was created. This
means that the addition or deletion of storage aras, logical
areas, and record caches invalidate the statistic files. This
restriction prevents incorrect statistic information from being
loaded when intervening physical changes occur to the database.
Closing the database updates the statistic files and makes
them valid. Use the RMU Show Users command to verify that the
statistic information file was imported.
4.6 – Wait
Wait
Nowait
Specifies whether the system prompt should be returned before
the database is completely open and available. Specify the
Wait qualifier if you want the system prompt returned when the
database is completely open and available. Specify Nowait if you
want the system prompt returned immediately, regardless of the
state of the open operation.
The Nowait qualifier is the default.
5 – Usage Notes
o To use the RMU Open command for a database, you must have the
RMU$OPEN privilege in the root file access control list (ACL)
for the database or the OpenVMS WORLD privilege.
6 – Examples
Example 1
The following command opens the mf_personnel database:
$ RMU/OPEN MF_PERSONNEL
Example 2
The following command opens the mf_personnel database in the
WORK directory, all the databases in the .TEST directory, and the
databases specified by the path names CDD$TOP.FINANCE and SAMPLE_
DB:
$ RMU/OPEN DISK1:[WORK]MF_PERSONNEL, CDD$TOP.FINANCE/PATH, -
_$ DISK1:[TEST]*, SAMPLE_DB/PATH
Example 3
This command opens the mf_personnel database, sets the total
global buffers for this opened instance of the database, and sets
the maximum number of global buffers that can be given to any
user. This example limits the number of users who can access this
database at any given time to 2 (Total divided by User_Limit).
You may want to increase the values of Total and User_Limit.
$ RMU/OPEN MF_PERSONNEL/GLOBAL_BUFFERS=(TOTAL=10,USER_LIMIT=5)
If you define a user limit value that is greater than the value
you specify for Total, you receive an error message:
$ RMU/OPEN MF_PERSONNEL/GLOBAL=(TOTAL=5,USER_LIMIT=10)
%RMU-F-VALGTRMAX, value (10) is greater than maximum allowed
value (5) for GLOBAL_BUFFERS.USER_LIMIT
Example 4
This command disables row caching.
$ RMU/OPEN MF_PERSONNEL.RDB /ROW_CACHE=DISABLE