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. 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.

Scope

ISQL or Application Programs

SQL Syntax

  START DBE 'DBEnvironmentName' [AS 'ConnectionName'][MULTI]
  [BUFFER = DataBufferPages, LogBufferPages) 
   TRANSACTION = MaxTransactions
   MAXIMUM TIMEOUT = {TimeoutValue [SECONDS 
                                    MINUTES] 
                      NONE                   } 
   DEFAULT TIMEOUT = {TimeoutValue [SECONDS 
                                    MINUTES] 
                      MAXIMUM                } 
   RUN BLOCK = ControlBlockPages]|,...|

Parameters

DBEnvironmentName

identifies the DBEnvironment in which the session is established. Unless you specify an absolute path name, the name you specify is assumed to be relative to your current working directory.

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. The default is 50.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 '../sampledb/PartsDBE'