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Berkeley DB: DbEnv::set_lg_max
DbEnv::set_lg_max
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#include <db_cxx.h>
int
DbEnv::set_lg_max(u_int32_t lg_max);
int
DbEnv::get_lg_max(u_int32_t *);
Description: DbEnv::set_lg_max
Set the maximum size of a single file in the log, in bytes. Because
DbLsn file offsets are unsigned four-byte values, the set
value may not be larger than the maximum unsigned four-byte value.
When the logging subsystem is configured for on-disk logging, the
default size of a log file is 10MB.
When the logging subsystem is configured for in-memory logging, the
default size of a log file is 256KB. In addition, the configured log
buffer size must be larger than the log file size. (The logging
subsystem divides memory configured for in-memory log records into
"files", as database environments configured for in-memory log records
may exchange log records with other members of a replication group, and
those members may be configured to store log records on-disk.) When
choosing log buffer and file sizes for in-memory logs, applications
should ensure the in-memory log buffer size is large enough that no
transaction will ever span the entire buffer, and avoid a state where
the in-memory buffer is full and no space can be freed because a
transaction that started in the first log "file" is still active.
See Log File Limits for more
information.
The database environment's log file size may also be set using the environment's
DB_CONFIG file. The syntax of the entry in that file is a
single line with the string "set_lg_max", one or more whitespace characters,
and the size in bytes.
Because the DB_CONFIG file is read when the database
environment is opened, it will silently overrule configuration done
before that time.
The DbEnv::set_lg_max method configures a database environment, not only operations
performed using the specified DbEnv handle.
The DbEnv::set_lg_max method may be called at any time during the life of the
application.
If no size is specified by the application, the size last specified for
the database region will be used, or if no database region previously
existed, the default will be used.
The DbEnv::set_lg_max method
either returns a non-zero error value
or throws an exception that encapsulates a non-zero error value on
failure, and returns 0 on success.
Parameters
- lg_max
- The lg_max parameter is the size of a single log file, in bytes.
Errors
The DbEnv::set_lg_max method
may fail and throw
DbException,
encapsulating one of the following non-zero errors, or return one of
the following non-zero errors:
- EINVAL
- If the method was called after DbEnv::open was called;
the size of the log file is less than four times the size of the in-memory
log buffer;
The specified log file size was too large; or if an
invalid flag value or parameter was specified.
Description: DbEnv::get_lg_max
The DbEnv::get_lg_max method returns the maximum log file size.
The DbEnv::get_lg_max method may be called at any time during the life of the
application.
The DbEnv::get_lg_max method
either returns a non-zero error value
or throws an exception that encapsulates a non-zero error value on
failure, and returns 0 on success.
Parameters
- lg_maxp
- The DbEnv::get_lg_max method returns the
maximum log file size in lg_maxp.
Class
DbEnv, DbLogc, DbLsn
See Also
Logging Subsystem and Related Methods
Copyright (c) 1996-2004 Sleepycat Software, Inc. - All rights reserved.
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