7.7 Connection Buffers Configuration Metrics

Lists the Connection Buffers configuration metrics and provides a brief description of each.

Table 7.7 Connection Buffers Configuration Metrics

Name	Description
Bulk Insert Buffer Size	Limits the size (in bytes) of the special tree-like cache MyISAM uses to make bulk inserts faster for INSERT ... SELECT, INSERT ... VALUES (...), (...), ..., and LOAD DATA INFILE, when adding data to nonempty tables, per thread.
Join Buffer Size	The minimum size (in bytes) of the buffer that is used for plain index scans, range index scans, and joins that do not use indexes and thus perform full table scans.
Max Allowed Packet	The maximum size (in bytes) of one packet or any generated / intermediate string from connections to the MySQL server.
Net Buffer Length	Each client connection is associated with a connection buffer and result buffer. Both begin with a size given by net_buffer_length (in bytes) but are dynamically enlarged up to max_allowed_packet bytes as needed.
Preload Buffer Size	The size of the buffer that is allocated when preloading indexes.
Query Alloc Block Size	The allocation size of memory blocks that are allocated for objects created during statement parsing and execution. If you have problems with memory fragmentation, it might help to increase this parameter.
Query Prealloc Size	The size of the persistent buffer used for statement parsing and execution.
Read Buffer Size	Each thread that does a sequential scan allocates a buffer of this size (in bytes) for each table it scans.
Read Rnd Buffer Size	The size (in bytes) for reading rows in sorted order following a key-sorting operation, to avoid disk seeks.
Sort Buffer Size	Each session that needs to do a sort allocates a buffer of this size (in bytes).
Stored Program Cache	Sets a soft upper limit for the number of cached stored routines per connection. The value of this variable is specified in terms of the number of stored routines held in each of the two caches maintained by the MySQL Server for, respectively, stored procedures and stored functions.
Thread Stack	The stack size for each connection thread.
Transaction Alloc Block Size	The size (in bytes) by which to increase the per-transaction memory pool use for connection transactions.
Transaction Prealloc Size	The initial size (in bytes) of the per-transaction memory pool from which various transaction-related allocations take memory.