FAQ: Difference between revisions

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'''Frequently Asked Questions'''
The midas documentation has moved. The new documentation about the topics on this page is in:
 
* [https://midas.triumf.ca/docs/develop/features/core_system/odb/configuring/#corruption Corruption] on the ODB: configuring page (recovering from a corrupted ODB)
There is a related page of [[Installation/Compilation problems|Common Installation Problems]].
* [https://midas.triumf.ca/docs/develop/features/core_system/odb/configuring/#enlarging-the-available-size Enlarging the available size] on the ODB: configuring page (resizing the ODB)
 
* [https://midas.triumf.ca/docs/develop/reference/reference/odb_keys/#system /System] on the ODB keys page (showing the run state in the odbedit prompt)
== Increasing Number of Hot-links ==
* [https://midas.triumf.ca/docs/develop/features/deployment/large_experiments/#more-than-256-hotlinks-in-a-program More than 256 hotlinks in a program] on the Large experiments page (increasing the number of hotlinks)
 
# Use odbedit to save current ODB
<pre>
odbedit
save current_odb.odb  
</pre>
# Stop all the running MIDAS processes, including mlogger and mserver using the web
interface. Then stop mhttpd as well.
# Remove your old ODB (we will recreate it after modifying MIDAS, using the backup you just
made).
<pre>
mv .ODB.SHM .ODB.SHM.20161104
rm /dev/shm/thomas_ODB_SHM
</pre>
# Make the following modifications to midas.  In this particular case I have increased the
max number of open records from 256 to 1024.  You would need to change the constants if you
want to change to other values
<pre>
diff --git a/include/midas.h b/include/midas.h
index 02b30dd..33be7be 100644
--- a/include/midas.h
+++ b/include/midas.h
@@ -254,7 +254,7 @@ typedef std::vector<std::string> STRING_LIST;
-#define MAX_OPEN_RECORDS      256          /**< number of open DB records  */
+#define MAX_OPEN_RECORDS      1024          /**< number of open DB records  */
diff --git a/src/odb.c b/src/odb.c
index 47ace8f..ac1bef3 100755
--- a/src/odb.c
+++ b/src/odb.c
@@ -699,8 +699,8 @@ static void db_validate_sizes()
-   assert(sizeof(DATABASE_CLIENT) == 2112);
-   assert(sizeof(DATABASE_HEADER) == 135232);
+  assert(sizeof(DATABASE_CLIENT) == 8256);
+  assert(sizeof(DATABASE_HEADER) == 528448);
</pre>
The calculation is as follows (in case you want a different number of open records):
DATABASE_CLIENT = 64 + 8*MAX_OPEN_ERCORDS = 64 + 8*1024 = 8256
DATABASE_HEADER = 64 + 64*DATABASE_CLIENT = 64 + 64*8256 = 528448
# Rebuild MIDAS
<pre>
make clean; make
</pre>
# Create new ODB
<pre>
odbedit -s 1000000
</pre>
Note, you should change the size of the ODB to whatever you need.
# reload your original ODB
<pre>
load  current_odb.odb
</pre>
# Rebuild your frontend against new MIDAS; then it should work and you should be able to
produce more open records.

Latest revision as of 22:00, 30 October 2026

The midas documentation has moved. The new documentation about the topics on this page is in:

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