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START DBE
The START DBE statement establishes a connection with a given
DBEnvironment and establishes a set of startup parameters that apply to
this and all subsequent connections until all connections to the
DBEnvironment have been terminated. Any startup parameters not
explicitly specified are taken from the DBECon file.[REV BEG] The changes
are only temporary for START DBE parameters; use START DBE NEW to specify
the start up parameters to be stored in the DBECon file in a new DBE. Use
SQLUtil to change the parameters in the DBECon file in an existing
DBE.[REV END]
Scope
ISQL or Application Programs
SQL Syntax
START DBE 'DBEnvironmentName' [AS ConnectionName'] [MULTI]
[BUFFER = (DataBufferPages, LogBufferPages)]
[TRANSACTION = MaxTransactions ]
[ {TimeoutValue [SECONDS]}]
[MAXIMUM TIMEOUT = { [MINUTES]}]
[ { }]
[ {NONE }]
[ ] |,...|
[ {TimeoutValue [SECONDS]}]
[DEFAULT TIMEOUT = { [MINUTES]}]
[ { }]
[ {MAXIMUM }]
[ ]
[RUN BLOCK = ControlBlockPages ]
Parameters
DBEnvironmentName identifies the DBEnvironment in which the session
is established. Name qualification follows
standard MPE/iX file naming conventions. Unless
you specify a group and account name, the name
you specify is assumed to be relative to your
current group and account. DBEnvironmentName
cannot exceed 36 bytes. You can also use an
MPE/iX back reference for DBEnvironmentName as
shown in the following example:
:FILE DBE = PartsDBE.SomeGrp.Acct
START DBE '*DBE'
ConnectionName associates a user specified name with
this connection. ConnectionName must be
unique for each DBEnvironment connection
within an application or an ISQL session.
If a ConnectionName is not specified,
DBEnvironmentName is the default. ConnectionName
cannot exceed 128 bytes.
MULTI indicates the DBEnvironment can be accessed by
multiple users simultaneously. If omitted, the
DBEnvironment can be accessed only by the user
issuing the START DBE statement. If the MULTI
option is specified, other users can start DBE
sessions by using the CONNECT statement.
DataBufferPages specifies the number of 4096-byte data buffer
pages to be used. Data buffer pages hold index
and data pages.
You can request up to 50,000 data buffer pages.
The minimum number of data buffers is 15. The
default number is 100. The total number of data
buffer pages and runtime control block pages
cannot exceed 256 Mbytes.
See the "ALLBASE/SQL Limits" Appendix in the
ALLBASE/SQL Database Administration Guide.
LogBufferPages specifies the number of 512-byte log buffer pages
to be used. You can request from 24 to 1024 log
buffer pages, limited by the amount of storage
available. The default number of log buffer
pages is 24.
MaxTransactions specifies the maximum number of concurrent
transactions that can be concurrently active.
You can specify a value in the range from 2 to
240. [REV BEG]The default is 50.[REV END] This
value overrides the maximum value stored in the
DBECon file. Any attempt to start a transaction
beyond the maximum limit waits for the specified
TIMEOUT and returns an error if TIMEOUT is
exceeded. For each user logged on to the system
at any point in time you should allow 2
concurrent transactions for just being connected
to the DBE.
MAXIMUM TIMEOUT specifies the maximum user timeout value. This
value temporarily overrides the maximum stored in
the DBECon file. When no value is specified, the
DBECon file value is the default.
DEFAULT TIMEOUT specifies the maximum user timeout value. This
value temporarily overrides the maximum stored in
the DBECon file. When no value is specified, the
DBECon file value is the default.
TimeoutValue is an integer literal greater than zero. If the
TimeoutValue is not qualified by MINUTES, SECONDS
is assumed. If representing seconds,
TimeoutValue must be in the range of 1 to
2,147,483,647. If representing minutes,
TimeoutValue must be in the range of 1 to
35,791,394.
ControlBlockPages specifies the number of runtime control blocks
allocated.
You can specify a value from 17 to 2,000 pages
for this parameter. The default is 37 pages.
The total number of data buffer pages and runtime
control block pages cannot exceed 256 Mbytes.
Description
* Any parameters (except the MULTI option) not specified in the
START DBE statement are assigned values currently stored in the
DBECon file (which has the same name as the DBEnvironment name
specified). The user mode in the DBECon file is always overridden
by the user mode specified in the START DBE statement.
* Normally, if autostart mode has the value of ON, DBE sessions are
established by using the CONNECT statement. The START DBE
statement is needed only to temporarily override DBECon file
parameters for the DBEnvironment, as when you need to start a
single-user DBEnvironment in multiuser mode or vice versa. When
you issue the CONNECT statement and autostart mode is on,
ALLBASE/SQL executes a START DBE statement on your behalf if no
sessions for the DBEnvironment are active. ALLBASE/SQL starts
your session using all parameters in the current DBECon file.
* If autostart mode has a value of OFF, you always use the START DBE
statement to start up a DBEnvironment. If the MULTI option is not
specified, the DBEnvironment is started up in single-user mode.
If the MULTI option is specified, the DBEnvironment is started up
in multiuser mode and other users can initiate DBE sessions by
using the CONNECT statement.
* Timeout values set in the START DBE statement remain in effect
only as long as there is a session established for connected
DBEnvironments and do not modify the values stored in the DBECon
file.
* If no MAXIMUM TIMEOUT limit is specified, the MAXIMUM TIMEOUT
limit stored in the DBECon file remains in effect. If no DEFAULT
TIMEOUT value is specified, the DEFAULT TIMEOUT value stored in
the DBECon file remains in effect.
* If MAXIMUM TIMEOUT = NONE, infinity (no timeout) is assumed. If
DEFAULT TIMEOUT = MAXIMUM, the value of MAXIMUM TIMEOUT is
assumed. The DEFAULT TIMEOUT value may not exceed the MAXIMUM
TIMEOUT value.
* No connections to the DBEnvironment can be in effect when this
command is issued.
* The START DBE statement is also used before using the START DBE
NEWLOG statement. Refer to the START DBE NEWLOG statement for
additional information.
Authorization
You can issue the START DBE statement only if you have DBA authority.
Example
The sample DBEnvironment is started in single-user mode. All parameters
except the user mode in the DBECon file are used for the duration of the
single-user session. After this session ends, a CONNECT statement can be
used to establish a multiuser session for this DBEnvironment, because the
user mode in the DBECon file is still multiuser and the autostart flag is
still ON.
START DBE 'PartsDBE.SomeGrp.SomeAcct'
MPE