<p>MySQL throws error 1738 when binlog_cache_size is set higher than max_binlog_cache_size.</p>
<p>MySQL Error 1738 ER_BINLOG_CACHE_SIZE_GREATER_THAN_MAX occurs when binlog_cache_size exceeds max_binlog_cache_size. Lower binlog_cache_size or raise the maximum, then restart or apply SET GLOBAL commands to resolve the mismatch.</p>
Option binlog_cache_size (%lu) is greater than
MySQL returns error 1738 when binlog_cache_size is configured with a value greater than max_binlog_cache_size. During startup or a SET operation, the server detects the violation, logs the error, and silently resets binlog_cache_size to the maximum allowed value.
The binary log cache temporarily holds transactional events before they flush to the binary log. Oversizing it beyond the server cap wastes memory and can hide tuning mistakes. Correct values protect memory budgets and keep replication stable.
The error arises when my.cnf or SET GLOBAL statements assign a larger binlog_cache_size than permitted. Parameter group templates in cloud environments frequently copy values between instance types, triggering the mismatch on smaller nodes.
Downgrading max_binlog_cache_size without adjusting binlog_cache_size also surfaces the error during the next restart. Configuration management drift and copy-paste mistakes remain the most common triggers.
Ensure binlog_cache_size is less than or equal to max_binlog_cache_size. Decide whether to decrease the cache size or increase the maximum, then apply changes in order and verify with SHOW VARIABLES.
-- Lower cache size only
SET GLOBAL binlog_cache_size = 65536;
-- Or raise the maximum first, then set cache size
SET GLOBAL max_binlog_cache_size = 67108864;
SET GLOBAL binlog_cache_size = 16777216;
-- Check effective settings
SHOW VARIABLES LIKE 'binlog_cache_size';
SHOW VARIABLES LIKE 'max_binlog_cache_size';
Cloud parameter templates often set binlog_cache_size for large transactions but later run on memory-constrained instances. Align template values with hardware capabilities to eliminate the error.
After upgrading MySQL, default max_binlog_cache_size may shrink. Review release notes, compare defaults, and recalculate memory before restarting production servers.
Keep binlog_cache_size in the 32K-2M range unless workloads demand larger transactions.
Automate configuration checks with CI scripts or tools like Galaxy that highlight server errors in real time.
Document parameter dependencies so future administrators adjust both settings together.
Version control my.cnf files to track intentional changes and detect drift quickly.
Error 1726 ER_BINLOG_CACHE_SIZE_TOO_SMALL appears when binlog_cache_size falls below the internal minimum; increase the value to resolve.
Error 1231 variable_is_readonly shows when attempting to modify max_binlog_cache_size in a read-only context; connect with SUPER privilege or edit my.cnf.
Error 1201 ER_MASTER_FATAL_ERROR_READING_BINLOG indicates replication I/O thread failure due to corrupt binary logs; run mysqlbinlog for manual recovery.
Administrators set binlog_cache_size to an unrealistically high number without raising the maximum.
Parameter templates copied from larger instances exceed limits on smaller servers.
New MySQL versions lower max_binlog_cache_size but retain previous binlog_cache_size values.
Raised when binlog_cache_size is below the engine minimum.
Occurs when changing dynamic variables without proper privileges.
Indicates replication failure due to binary log corruption.
Yes, max_binlog_cache_size is dynamic in MySQL 8.0 and later, but requires SUPER privilege.
Choose a value that comfortably fits the largest transaction, typically 32K to 2M for most OLTP workloads.
No, MySQL starts normally but resets binlog_cache_size to max_binlog_cache_size and logs the error.
Galaxy surfaces server errors instantly in the editor output, letting you spot misconfigured variables before pushing to production.
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