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Table of Contents
1. General Information
2. MySQL Installation
3. Tutorial Introduction
4. Database Administration
5. MySQL Optimisation
6. MySQL Language Reference
7. MySQL Table Types
8. MySQL APIs
9. Extending MySQL

Chapter 7: MySQL Table Types 535 which your changes will not be committed until you execute COMMIT (or decide to ROLLBACK the changes). The following options to mysqld can be used to change the behaviour of BDB tables: Option Description --bdb-home=directory Base directory for BDB tables. This should be the same directory you use for {datadir. --bdb-lock- detect=# Berkeley lock detect. One of (DEFAULT, OLD- EST, RANDOM, or YOUNGEST). --bdb-logdir=directory Berkeley DB log le directory. --bdb-no-sync Don't synchronously ush logs. --bdb-no-recover Don't start Berkeley DB in recover mode. --bdb-shared-data Start Berkeley DB in multi-process mode (Don't use DB_PRIVATE when initialising Berkeley DB) --bdb-tmpdir=directory Berkeley DB temple name. --skip-bdb Don't use berkeley db. -O bdb_max_lock=1000 Set the maximum number of locks possible. See Section 4.5.6.4 [SHOW VARIABLES], page 257. If you use --skip-bdb, MySQL will not initialise the Berkeley DB library and this will save a lot of memory. Of course, you cannot use BDB tables if you are using this option. Normally you should start mysqld without --bdb-no-recover if you intend to use BDB tables. This may, however, give you problems when you try to start mysqld if the BDB log les are corrupted. See Section 2.4.2 [Starting server], page 96. With bdb_max_lock you can specify the maximum number of locks (10000 by default) you can have active on a BDB table. You should increase this if you get errors of type bdb: Lock table is out of available locks or Got error 12 from ... when you have do long transactions or when mysqld has to examine a lot of rows to calculate the query. You may also want to change binlog_cache_size and max_binlog_cache_size if you are using big multi-line transactions. See Section 6.7.1 [COMMIT], page 482. 7.6.4 Characteristics of BDB tables: To be able to rollback transactions BDB maintain log les. For maximum performance you should place these on another disk than your databases by using the --bdb_log_ dir options. MySQL performs a checkpoint each time a new BDB log le is started, and removes any log les that are not needed for current transactions. One can also run FLUSH LOGS at any time to checkpoint the Berkeley DB tables. For disaster recovery, one should use table backups plus MySQL's binary log. See Section 4.4.1 [Backup], page 227. Warning: If you delete old log les that are in use, BDB will not be able to do recovery at all and you may lose data if something goes wrong. MySQL requires a PRIMARY KEY in each BDB table to be able to refer to previously read rows. If you don't create one, MySQL will create an maintain a hidden PRIMARY

MySQL Reference Manual

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