diff options
Diffstat (limited to 'src/util/db2/man/db_log.3')
| -rw-r--r-- | src/util/db2/man/db_log.3 | 290 |
1 files changed, 290 insertions, 0 deletions
diff --git a/src/util/db2/man/db_log.3 b/src/util/db2/man/db_log.3 new file mode 100644 index 0000000..34c4d1f --- /dev/null +++ b/src/util/db2/man/db_log.3 @@ -0,0 +1,290 @@ +.\" Copyright (c) 1990, 1993, 1994, 1995 +.\" The Regents of the University of California. All rights reserved. +.\" +.\" Redistribution and use in source and binary forms, with or without +.\" modification, are permitted provided that the following conditions +.\" are met: +.\" 1. Redistributions of source code must retain the above copyright +.\" notice, this list of conditions and the following disclaimer. +.\" 2. Redistributions in binary form must reproduce the above copyright +.\" notice, this list of conditions and the following disclaimer in the +.\" documentation and/or other materials provided with the distribution. +.\" 3. All advertising materials mentioning features or use of this software +.\" must display the following acknowledgement: +.\" This product includes software developed by the University of +.\" California, Berkeley and its contributors. +.\" 4. Neither the name of the University nor the names of its contributors +.\" may be used to endorse or promote products derived from this software +.\" without specific prior written permission. +.\" +.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND +.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE +.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE +.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE +.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL +.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS +.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) +.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT +.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY +.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF +.\" SUCH DAMAGE. +.\" +.\" @(#)db_log.3 8.15 (Berkeley) 8/3/95 +.\" +.TH DB_LOG 3 "August 3, 1995" +.UC 7 +.SH NAME +db_log \- log-manager access method +.SH DESCRIPTION +.so db.so +.GN +specific details of the logging access method. +.PP +These functions provide a general-purpose logging facility sufficient +for transaction management. +Logs can be shared by multiple processes. +.PP +A log is represented by the directory, +.IR "not the file" , +named by the first argument to +.IR db_open (3). +The first argument must be non-NULL, +and the directory must already exist +.I db_open +is called. +In that directory, the log is stored in one or more files named +in the format ``log.YYYY.MM.DD.HH.MM.SS'', where ``YYYY.MM.DD.HH.SS'' +is the approximate creation time of the log file, and is guaranteed +to be unique in the directory. +.PP +The group of the created files is based on the system and directory +defaults, and is not further specified by the log access method. +All files are created with the +.I mode +specified to +.IR db_open , +(as described in +.IR chmod (2)) +and modified by the process' umask value (see +.IR umask (2)). +.PP +The +.I flags +argument to +.I db_open +must be 0 for the +.I db_log +access method. +.SH "ACCESS METHOD SPECIFIC INFORMATION" +The log access method specific data structure provided to +.I db_open +is typedef'd and named LOGINFO. +A LOGINFO structure has at least the following fields, +which may be initialized before calling +.IR db_open : +.TP 5 +off_t max_file_size; +The maximum size of a single file in the log. +If not specified, the maximum size defaults to an implementation-specific +value. +.TP 5 +int lorder; +The byte order for integers in the stored database metadata. +The number should represent the order as an integer; for example, +big endian order would be the number 4,321. +If +.I lorder +is 0 (no order is specified) the current host order is used. +.PP +If the log already exists, the values specified for the parameters +max_file_size and lorder are ignored in favor of the values used +when the log was created. +.SH "DB OPERATIONS" +The data part of the key/data pair used by the log access method +is the same as for other access methods. +The key is different. +Each log record is identified by a log sequence number (LSN), +which is stored in a DBT, and which is used as the +.I key +for all log functions that take +.I key +arguments. +Applications cannot create LSN's, and all LSN's provided to functions +as arguments must first be retrieved using the +.I put +or +.I seq +functions. +To provide a distinguished value for applications, it is guaranteed that +no valid LSN will ever have a size of 0. +.PP +Applications can compare LSN's using the +.I log_lsn_compare +function (see below). +.PP +Applications can associate LSN's with specific log files. +The function +.I log_lsn_file +(see below), returns the name of the log file containing the +record with a specified LSN. +(The mapping of LSN to file is needed for database administration. +For example, a transaction manager typically records the earliest LSN +needed for restart, and the database administrator may want to archive +log files to tape when they contain only LSN's before the earliest one +needed for restart.) +.PP +Applications can truncate the log file up to a specific LSN using the +.I log_trunc +function (see below). +.PP +The functions returned by +.I db_open +for the log access method are as described in +.IR db_open , +with the following exceptions and additions: +.TP 5 +type +The type is DB_LOG. +.TP 5 +del +The +.I del +function always returns an error for the log-manager access method, +setting +.I errno +to EINVAL. +.TP 5 +int (*log_flush)(const DB *db, const DBT *lsn); +The +.I log_flush +function flushes the log up to and including the log record +.IR lsn . +.RT log_flush +.TP 5 +int (*log_lsn_compare)(const DB *, +.ti +5 +const DBT *lsn1, const DBT *lsn2); +A pointer to a function which is provided to permit applications to +compare LSN's. +The +.I log_lsn_compare +function returns an integer less than, equal to, or greater than zero +if the first LSN is considered to be respectively less than, equal to, +or greater than the second LSN. +.TP 5 +int (*log_lsn_file)(const DB *db, +.ti +5 +const DBT *lsn, char *name); +.br +The +.I log_lsn_file +function stores a pointer to the name of the file containing +.I lsn +in the address referenced by +.IR name. +This pointer is to an internal static object, and subsequent calls to +the same function will modify the same object. +.IP +.RT log_lsn_file +.TP 5 +int (*log_unlink)(const char *path, int force); +The +.I log_unlink +function destroys the log represented by +.IR path . +If the +.I force +parameter is not set to 1 and there are other processes using the +log, then +.I log_unlink +will return -1, setting +.IR errno +to EBUSY. +If +.I force is not set or there are no processes using the log, then all files +used by the log are destroyed. +.I log_unlink +will return -1 on failure, setting +.IR errno , +and 0 on success. +.TP 5 +int (*log_trunc)(const DB *db, const DBT *lsn); +The +.I log_trunc +function truncates the log up to an LSN which is less than +.IR lsn . +.RT log_trunc +.TP 5 +put +A log record containing +.I data +is appended to the log. +Unlike the +.I put +functions for other access methods, the key parameter is not initialized +by the application, instead, the LSN assigned to the data is returned in +the +.I key +parameter. +.IP +The caller is responsible for providing any necessary structure to +.I data . +(For example, in a write-ahead logging protocol, the application must +understand what part of +.I data +is an operation code, what part is redo information, and what part is +undo information. +In addition, most transaction managers will store in +.I data +the LSN of the previous log record for the same transaction, +to support chaining back through the transaction's log records +during undo.) +.IP +The parameter +.I flag +must be set to 0 or exactly one of the following values: +.RS +.TP 5 +R_CHECKPOINT +Specify the key/data pair of the current call as the one to be returned +when the +.I seq +function is next called with the R_CHECKPOINT flag. +.TP 5 +R_FLUSH +Flush immediately (ignoring any possibility for group commit). +.RE +.TP 5 +seq +The +.I seq +function takes the following additional flag: +.RS +.TP 5 +R_CHECKPOINT +The last key/data pair stored by the +.I put +function (using the R_CHECKPOINT flag) is returned, +and the cursor is set or initialized to reference it. +The expected use of this flag is during restart and to determine what +part of the log must be available for restart. +Therefore, the log record retrieved with R_CHECKPOINT should contain +all the information that the transaction manager will need for this +purpose. +.RE +.TP 5 +sync +The +.I sync +function always returns an error for the log-manager access method, +setting +.I errno +to EINVAL. +.SH "SEE ALSO" +.IR db_btree (3), +.IR db_hash (3), +.IR db_lock (3), +.IR db_mpool (3), +.IR db_open (3), +.IR db_recno (3), +.IR db_txn (3) |