Update the header comment on the memjournal.c file. No code changes.

FossilOrigin-Name: 07f10deabb0f4207408142541e3913d638dfcdeb

manifest

@@ -1,5 +1,5 @@
-C Performance\soptimization\sthe\sVdbe\sallocator.
-D 2016-04-12T00:26:59.031
+C Update\sthe\sheader\scomment\son\sthe\smemjournal.c\sfile.\s\sNo\scode\schanges.
+D 2016-04-12T11:58:18.868
 F Makefile.in eba680121821b8a60940a81454316f47a341487a
 F Makefile.linux-gcc 7bc79876b875010e8c8f9502eb935ca92aa3c434
 F Makefile.msc 71b8b16cf9393f68e2e2035486ca104872558836
@@ -347,7 +347,7 @@ F src/mem1.c 6919bcf12f221868ea066eec27e579fed95ce98b
 F src/mem2.c f1940d9e91948dd6a908fbb9ce3835c36b5d83c3
 F src/mem3.c 8768ac94694f31ffaf8b4d0ea5dc08af7010a35a
 F src/mem5.c 9bf955937b07f8c32541c8a9991f33ce3173d944
-F src/memjournal.c 2815ef7684671d93a1ec6a31e1e63c45de4b4d31
+F src/memjournal.c 95752936c11dc6995672d1dd783cd633eea0cc95
 F src/msvc.h d9ba56c6851227ab44b3f228a35f3f5772296495
 F src/mutex.c 8e45800ee78e0cd1f1f3fe8e398853307f4a085c
 F src/mutex.h 779d588e3b7756ec3ecf7d78cde1d84aba414f85
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-Z 22234bdd82888c7db3f11967733fa3c5
+Z ca7267cbdba15c8e817fe9239b1f31a1

manifest.uuid

@@ -1 +1 @@
-e2c4995bf1099cc02bcb1dc4a4631f06a870d171
+07f10deabb0f4207408142541e3913d638dfcdeb

src/memjournal.c

@@ -13,6 +13,15 @@
 ** This file contains code use to implement an in-memory rollback journal.
 ** The in-memory rollback journal is used to journal transactions for
 ** ":memory:" databases and when the journal_mode=MEMORY pragma is used.
+**
+** Update:  The in-memory journal is also used to temporarily cache
+** smaller journals that are not critical for power-loss recovery.
+** For example, statement journals that are not too big will be held
+** entirely in memory, thus reducing the number of file I/O calls, and
+** more importantly, reducing temporary file creation events.  If these
+** journals become too large for memory, they are spilled to disk.  But
+** in the common case, they are usually small and no file I/O needs to
+** occur.
 */
 #include "sqliteInt.h"