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Oracle LOB 类型及SecureFiles

时间:2020-09-04 04:12:03   作者:酷酷娱乐网   来源:www.kukuyl.com  
内容摘要:
根据一些经验,发现数据库中有LOB(large object)类型字段,往往会伴随一些数据库的问......

根据一些经验,发现数据库中有LOB(large object)类型字段,往往会伴随一些数据库的问题出现。有些人对LOB字段的用法存在着误解。下面简单说说LOB 类型。

先说Oracle支持的4中类型

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" alt=""/>


简单的概括就是 CLOB 和 NCLOB 保存文本信息,BLOB 保存二进制信息。

存储结构:从Oracle 11g 开始,引入了SecureFiles 新的LOB 架构11G 之前叫BasicFiles.在Oracle11G中如果不特别指定,默认是会创建成BasicFiles LOB.但是在Oracle12C之后,LOB列在ASSM管理的表空间.默认都会是SecureFiles .


SecureFiles的好处是:

  1. Oracle官方文档已经说明,BasicFiles在后续版本将不能使用。

  2. 管理更加简单CHUNK,FREELISTS,FREELISTGROUPS等参数不在支持。

  3. SecureFiles 支持加密,压缩和去重.



强烈建议使用SecureFiles 而不是BasicFiles.


  • 创建SecureFile LOB

CREATE TABLE T_LOB (ID INT PRIMARY KEY, TXT CLOB);

  • 查看是否为SecureFiles


必须使用TORE AS SECUREFILE 字句创建表:

CREATE TABLE T_LOB_SECURE (ID INT PRIMARY KEY, TXT CLOB) LOB(TXT) STORE AS SECUREFILE;

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alnD0iYxXCr378/piFr1crv09kzi33hShsOzYatYbDiqcktSE+yR0lZRLHUeuyO/LvuO1Yude9tO9NRK7kHK2tUKXPi0cxG6Kx7bJzxDDskdZmrJpxIYTeti5jNkQ5N5/Sh4f29sJLK9PaqZEkBnveMpyh8fP1w7i9JOEO/y060GyIfBLm1MEAeB3Vj997PQyHb1tTTnlKY9KrS2K012iIShJTwX8V/DzC70P541p7JfL7pOW+8G2O8Ux/LenbiueY1C61t8xSyZqGJmJL3cyGlzzDhvOSms3CKK1NS1K/t9kQldYXwzC/pVB+MdzL1yt9s+FVOi6E0NvWpcxGjkofHjIWr9BU+O/D8nDMezUmq2/LbIhWhiNUpdEQlaxbLJ+MebVM9EId0Y/fZ35vanVqJW0Kvn3RnnqhxoTXlsRKDIaX1saWcvZIOHb/1Y/fH7Pw9faq9b4I91yutHZild4rteN7lTsG6X/LbPT+nQ3Xj1yfwTW6qaC+1qYlqX+/F8jeFI3/Hr5zOusXxI8wGwih96UssyFffUIeKqdMjIaXb3OPSh8e3lSE5kKOy9e4zI+5hUoTgytJNRw7jIaoZN00eSPQwwCEOqqfcB9q5TWS9gT56rWnXijNYGjSzs1VSWIq+K+Cn0f4fSh/XGvvUVV6zY2xkn25lFY3VyVregmz4SXXZ46Cc7Q2LUl9fw8Y/jdpbGf4zmn+9yRvNkRamy0khmGPtDYRQijLbNTq3sY5bzZEMg65qXtzESZ5/t/+mHb+e9XCcOw0GqLSddPUwwCEpnBL2vlXkr/uQu2pFyo0Epq52Gs0RKWJoRCO3x+zyJnnI6nmmhNzEfLuzIY8C6bnQZaC+lqblqS+/wGXlxD+2z+XtGNamy0khoE3Gwih1to0Gym1+m9nlKjuATreqP0bjFC+TDvvvcsZjgZGQ1SzbkdIDEyutPPfi2Iz0cJcxCrdI3Ldevx1vCWtnUdV3b1SktmltHq5Kk72C6W1E6pmTzl5E7GlzHHEknPEOJRS01eJMBsIoR7KMhvWmwnLbLR8kxFrT9LqHwyhtHqovfasG3ofqkuOuY4tXeGaO3sMtf2Hz4iUtHNzpLWVI62tlhLDsEdamwghlPExqvvvXISSMm82tHJR2E4rkbS+TbFuaEvskba6QjzPHgN7CiGEzte7erOBzhPrhrbEHmmrK8Tz7DGwpxBC6Hzt+p2NM8TD422KdUNbYo+01RXiefYY2FMIIXS+MBvoELFuaEvskba6QjzPHoPv/+/++3+7/f2//P3b7Q/+we32+78YJF/R6RrW4+//xT+9/b//+o26fgihxxBmAx0i1g1tiT3SVleI59ljcP3/r/8xJLUYjGvrF7ff/fF/VtcQIfT29ebMBkIIIZSr2z//J0pyiy6nP/iH6vohhN6+MBsIIYQeVmFC+7s//i+3v/3rL2o9dLz+7n//z8X6aHUQQm9fmA2EEEIPq/H3NEb97W/+r1oHnaf779D8Qi1HCL19ObPx7ec/QwghhB5O3miItHJ0rlgfhB5fs9kAAAB4OIJkFi4I6wPw8Ow2Gx8/fpy+60Pv9qEdspdqYZ0fD/YDHIm53zKSWfZbH7LuAcb6sCYA+7nKc3hlNuTfJfKD0cpaqHf7qK1q1kr+PCXr/JiqWVP2A6qVtmfCZDYuE7Hf+morrtr6sCYItVPNdRRegy3AbKCmqlkrHiyPq5o1ZT+gWml7RktmQ7Hf+morrtr6sCYItVPNdYTZQJdWzVrxYHlc1awp+wHVStszWjIbiv3WV1tx1daHNUGonWquI8wGurRq1ooHy+OqZk3ZD6hW2p7RktlQ7Le+2oqrtj6sCULtVHMdvXuz8e3XH24fPhj6+tvFub/97Q+3b74ajn/1ze2HxfFRP3zz1aqNr775YVHH9bdqd5R2/ocPX92++WFdN9Q4B72ea1PtLz2XVJujvr19LeML2q4df0rhWuVq68GyHufXt2+jOqt9ocTJXssxtl9/Gx8f9O3Xi7Zq4ly33kvVtXH+nrHWNCVtP4xjNbSa+/nX/Wq8QVvruVjxS8/Daz2e+/VRul5eqb3h2nxD+01LZkOl7j+pdcwdm70+pfedSNEabI1Ha0P6Xpw39enqqmvcZk1CaevTe01cfON6QTtjH/acavZqqk137tSWtk6zjDXxyu1jqfOvW9RX2nW0pXdvNkK5iyB18f3wze2rr766fZV78Un94aIIb/6pPuyLN635ZqJc3GabG3PxbcZJk5e0K+eHbdeOPyVrrVKyHyzTTTA2F8OD4r5G040uiuUYj+V59lqWP/RL4ly13pGq2rjAnlmv6bZSiYbIXsdJp173056Nyr/9ZrmHwpi79rSxbswj5/ooXS+vR9pvWjIbSt9v2+u4Pbat9Sm87yz6Gu97q32UGE+870K5c5P9RXWT815qGde1tPU5fE0knvH8G+9V32bJNZVaB001fVzhukV9tbyO8oTZCLR1IUq5XCBWPe2CiOum+qi9oMZxfbN6WIisNrfm4srlgl/dREXjDfaIG4K1VilZyaUbn3LTDOXiYdSJY2XFrvShXxpnd07heseqaWM859w9E69pjvaaja15a3OI66b6SMbAGRfLHIzy47sfm2IdrWvWPDauj9L18hr7foz9piWzodT9lrGOW2PbXp+y+07cV9z+1nj8+mhlcVvWGoq2+om1iKsibX3OW5NRPfbqGP/ya6ok1rV9nH3dor5aXEeZwmwESl+I8pOf6cbkblLrC0W7IPyFF/7b6qP2gpr7kAdKNC69ze25jG1+qz+8pgfXt1HbPW4I1lqlpCeX40/u1AfxrI060cPJXsuyh35pnMvXe623umeWa5qnfWbj7Ot+e9/Gfc0P7MWxrXls9yMqXS+veYwPsN+0ZDZU7f1n7z5oYjYKYrXed3e5czf682qxJqG09TlvTUb12Ktz/LOvqfQ6aCrv4xrXLeqr5XWUJ8xGoOSFuLhZ6zf11QWhXKCpPmovqPmGMH0ftqG2mTEX36Y7P3horMq2+topa61SUh8sylqstFln+XCx17LUbJTF2R/339esQXEbF9kzizXN1C6zkTHv1RyUfZTqYysGrnzYd369YvnY3o8p49yahzJmTaXr5RWOMY6F2uaF95uWzIay9pvrO7GOybFlrY8eJ6dFPNdrMCaGU5I4HduKVbimsdy5qf4CtViTUNr6nLcmo3rs1TD+cXytc1ProKm4j4tct6iv4usoR5iNQKkLMbzoRNrmd8eGG1co7UKz+tDOjy9GTYuxRQ8NbZw5c7nXCX5SIWXBTyvi82rHn5K1Vim9RbNREufS9dZU2sai/madfntmsaaZ2mM2cuatzaH5de9iOJaF4xHFY3R9Rft4cx6ZiVPpenkt+n/j+01LZkMl91tiHZNjy1qfQrOh9RNoK1arNoLxuXPjunv2fyA1roG09TlqTZb172U99uq9Td9O+poSpdZBU2kfi/qbdfpdt6iv1OtoQ5iNQOaFGF1k1rH1hTXe/MNjqYtduzBzpF7g04W4ajNzLmGb4fdhe3HbteNPyVqrlN6m2ciPc1hvLrfW21BRGxfaM4s1zVS12cic93oOHa97t0eVtlMP4Zx55Fwfg0rXyyvcDyLXzhvdb1oyG2prvzkp65gcW9b6FJqNua/lfc1rK1bxmoZy55r9KXUT/cRKxnWQtj6Hr4nbr/eyHns1jr+rb11Tk1LroKmojwtdt6ivkteRIcxGIOtCdBvdP8gjrS7E+PzoYktd7LUXVHxD8A8POaZetNEcvMI2Fm3ON055mN3norZdMf6UrLVKSX2waDfCWFt1stdyfOgv12SS8tAvjXPJelt6q3tmsaaZqjUbufNW55C9V8pjoLW9XMulsuYRtWmpeKyTHmm/aclsqKzEVhTFPDm2rPUpu+8s+lIS561YpfadO/etmQ1RqzWZ9+P47x57dR3/7edAah00lfTh/h1cq6HCNnrEAh2rzetIEWYjkH4h2jdwdwEEN1T1glBuOtZFU3tBrW8Ig6aHxzeLNvPnsmxzPO/rr5cPrHi8teNPSTZojdbrPM5ha3yp9YnLatZSa6M0zstzJqnrbSu/jWvtGW2tc/RY1/34wA/fsGnjHJU7j7He1jjKxzrqkfZbmMxq5aK859hyHdNj27c+8f5b78d13Ldildp37txoray2WqxJKGt92q9JYl4ps9For6rx33gOpNZBU34f17puUV+F11WJ/DXYgsczG+6mkfrpRerGtH5ApC722gtKvSFMx91PFnybBXNZteluMMtjV74h6Os8PkjCm5rTMDc/77lONI8xlveHx3zMmm8UTycXw2X8a+K8Oic4vljvhLLbeJA982ave+krKnP1zUQmUsE8cq6P2vWyxujiIn36NgvGu2rzoP0WJrNauWi13zLWcXtsGfev1ZqO5dp9Z9VXVG9rPKl9586NEkyrrRZrEspan0PXxK1D4hptsFet+LtYy5iUc1ProCm7Dzffa1+36Hz5a7AFD2c23LH4RjJrmVS4C0IuwFBae3GdqX31/EGLB4ei1cXrNV3kfgwlc1m3KTfVZbKt3hCiseeMv4fsdZ7mGY5xFROlTrSOotRaujo+/rPWN+OaOOeud0q5bbg5PsCeebvX/ZTMLLSM6Truy7LceSyOhf0F59eulznGN7jfrGQ21Hq/ba9j3tjS6+OUed+J9+jcdta+tNd0cd7UlusvaCMsa7Emoaz16bcm+vzCOj32qhX/1HPAjVM5bim3D9fuxa9bdL78NdiCN2020OOIdUah2A+olaxkNhT77TxZ68OaIHSu/DXYAsxGF2k/gcHZp8SDhT0Tiv3QW+9nv1nJbCj223my1oc10cRzAh0nfw22ALOBLiHWGYViP6BWspLZUOy382StD2uC0Lny12ALMBvoEmKdUSj2A2olK5kNxX47T9b6sCYInSt/DbYAs4EuIdYZhWI/oFayktlQ7LfzZK0Pa4LQufLXYAsWZkMaRgghhB5FYTKrlaNzxfogdF21YvVmo5SWg9GQX3yCx+dXv/rV9B0A+wEaEiSzFuy3EzHWhzUBOJeW12Czj1H95je/6SLMxvuABwuEsB+gGUYyG8J+OxFjfVgTgHPBbMCl0faJJQ8PlsdFW3dLHvYD1LLaU0EyuyqbYL+dSLA+IawJQDvie19KHswGXBptn1jy8GB5XLR1t+RhP0Atqz0VJLOrsgn224kE6xPCmgC0I773peTBbMCl0faJJQ8PlsdFW3dLHvYD1LLaU0EyuyqbYL+dSLA+IawJvHten29PL1+mfyhslQfE976UPIeaDUn242Oh6s3Gn97+cGj7wy8/3v5SLR8Vm43X5/V/OXPW8+tUS8edm1MnbPPp5RYv5ZeXp2WdQbkLLqz6CMaktf3hw9Mtbn5d7/k2tvLl9vL04aZOc9iY4XzUWEYn5o4nRNsnljzxpt5cZ5nL8P16nq+356nOZhtwCNq6W/IU74eB3Osydf1p5O6j7XanvancU6Adqz0VJLOrsgl1vyn7wu2xaf1y7o2le+1dEqxPiJXoWDHNWTOhZk2stkNW7e7IHRZtKe30Lh9qJO9V1e1Pz21Ny/Dm3SvHeOr5yDrWPkca6R3DZPmXl9uTL3Najk2Ixx/vk63ymPjel5LncLMhio97lZuNv7x9/KW0+cvh3D8sNhshbjEzbhSedH19c48bZrkR3CKH7UwbZ3sooxGIx/D6cu9z1faKqY14cw4X8XhaodlYVBxjEG7a7fGs0faJJU9qU1vr5o5H6+XGa134hfOANmjrbslTsx+2r8vt628Lve+tdv01OzwUX5bXILRntaeCZHZVNrHab27vxEnMeH/0y5y+N+7fa++GYH1C1veAjZhurln9mqSfH21zh+UzbD3mvuXTvxP3qr39r1jkJdv9z0jsnp6UNfdtWDnS9hj7lsu/l2NzeyWY63z+MOYxH3sd4uFLt8s14ntfSp5TzIZlOHZ9jOpPr2M24sUOic9zCx21kzUW9Wa4RGs7ZLmJNcaNrTaxaTbW7W+NR8PvjXDPWN97apLLoWRpjhLxzVof6IK27j32w+Z1mXH9baH2XdJudA1Ce+J9FSaz4XFXNqHtt3iti+6NDfbauyFYn5DVmmTENLlmO9bEuucIrsy4ptXxRO0s6ywNrcON2yenvcsD1HtVw/YnZP7qT+WT90qf50h/yzWNr9M1e+fQPgZjuZ/HODcXk9lMhGyV6/h7XqvncClFZiMcjNdjmA1lc4QsNoL8U79hbC/6Rj8DyQdYxvl+I6p1ootXi0fcf3o8OvEeSclTZzYGZE7TRZyql2wDuqKtuyVPS7Nxvy5zrp80et8F7SYfoNCC1Z4KktlV2YS63xYJwvq+uv9eDY5gfULWa5IR0+Sa1a+J/fzYaLM0d1iM3xP00bs8RLtXtWzfIWWGAUzcK+9xjM9P9TXRO4bFMRhYnNPXbOTIc6rZEIXlD2E2ZFOvNkfIcqOsbhib599x5w5tWRsk+QDL6meH2XAbfnnhJ8djEO6PLXmqzYa/8J4krnZsSvcKtENbd0ueJmZDuV62rr8tkn3ntBtdg9Ce1Z4KktlV2YS+35YP9Xjdtu6Ne/fauyFYnxBtTbZjmrFmFWtiPj+Ue8ySwtxBvT8Ez/Te5SFa3ZbtD7h4rOpPqG0NLBJziW+Qs8g5yfUY2DuHveUa8Tnyb9k3z4aZ2CpXiO99KXlONxsiX/5uzUYQC1HBMKSB4WIZz4s3itb2vAk3xykkNnW0oV08tH4CkuMxCPfPljz1ZmNgimfqoivdK9AObd0tearNRrRX1SVPXH9bJPdRTrvRNQjtWe2pIJldlU2Y+21ar5dh3eNlz7o37thr74ZgfULMNdmKaWLNHBVrYl73m8/kwtxBvT+Mz3Q31t7lIVrdlu1Px9U1EhJt3c9pazaaxHCrfEU0B8+8T5UyYas8Ir73peQ53WyE5bzZEMaNVDIWh+t3ed667YDNcQrjWNQmootgGY/lHD3J8TSk3mxMFzFvNh6KarOxOL5xXSrX3xZZ+yjVbnQNwgEYyWyIvd+mPaSsWdG9sWKvvRuM9dlMdMyY2mu2oGBNzOvetdEwd1DvD2MdV6V3eYhWt3X7qdgpba3j19ZsZM1hb/mCcX/oJmRgaGvMbYw6W+U7OdVsxOUPYTacQ0y4w6hcfchstWGR07Ynq49xU1sbM7wIVvGQ8uhCLXqg7qDWbLjxuTmN87bqle4VOJc2ZmOg8NreInsfWe2qDyLoipHMhqT2m3UPLL43Fu61d4OxPlmJjhHT7LXJXBPzut86PyrfvEcpz+Dh4N2w9C4P0e5VDdvfvJeu+p+e8UNbmlzOk7Oee+fQLAaJXM0ztOXK1TYHtsp3cprZiMtEj/EL4mVl9g2jZrGXmzB9k0wn1B6rjXge6zmvN3/2TXsnVWbDxTy4gON/B6TWF65HW7ORui61h4BN/j4y2pWHAmbjWIxkNuQQs1G4194NxvrkJTp6TPPXJm9NUtd9Sdn2PUrGEyXLh5YHqPeqVu0r9WKy7pVxOzk50t457C0XMoyG4M2EGsOBrfKdnGI24uNej2I2xg2yLnfnRIu4vmHkmQC3IaI6rq2g/e2b5DRO5ScO82lu40U3ULlwowtAjUdUL/+mvY/y5FKPuaur3KDSaw9Xo43ZiPZIxvW3hdp3SbtyfWE2jsVIZkOam40Ge+3dYKzPak0KYqquzY41ST8/2uYO7rz5HrFOSnuXzxj3qhbtuzgobS/Iulcqib1fj/jcoT0f5t4xTJeP/7b3k5RP+2YYs5y3bi9V3o7DzUZ8LFSN2fjTPxwCI5thoV/ePv7luq6UWbgAmwu2xtWP+10s0LQJwnKl/fEGtV1vzXQRLKTcjFZ14p+8KOOMN5rcWMPy1QVpxW9qe2ovbzz7KU0ux7XUHhKJG3/rQUM3qs1GtE+X9bavvy30vrfbHfdrrPU1CR0wktmQarOxWlN/b9y/194Nxvqs1yQ/pvqa1a+Jev12zB0W/R1crs5V+0GlLyvuf4xVmJyH5PR/R9ZUK9vOkfbNYUe5mCh/fKH7Xlztk2jsW+WtONRsbGnXm40MSSDh8Wm5qeHtw36AZhjJbAj77USM9WFN4N0zvbkw2SrfCWbDRPvJxSjFeHbiCmN4e/BggZDj9wPX7cNiJLMh3H9OxFifY9eE6x8uCGbjLt5sQAt42EMI+wGaYSSzIey3EzHWhzUBOBfMBjwcPFgghP0AzTCS2RD224kY68OaAJwLZgMeDh4sEMJ+gGYYyWwI++1EjPVhTQDOpZvZEONwNYnZkAkjhBBCpQqTWa0cnSvWB6HrqhWrNxsAAAAPQ5DMwgVhfQAeHswGAAA8LiSz14b1AXh4MBsAAPC4kMxeG9YH4OHBbAAAwOMiSewfkMxeFtYH4OHBbAAAwOMiSazXb/7PdBAuwe9+t1wfAHhIMBsAAPC4/LN/FCS0vwi+R+crWg8AeEgwGwAA8Lj8p/+wTGjRNfVv//W0YADwaGA2AADgsfn3/y5IbHm7cS0N6/Fv/tW0UADwiGA2AAAAAACgC5gNAAAAAADoAmYDAAAAAAC6gNkAAAAAAIAuYDYAAAAAAKALmA0AAAAAAOgCZgMAAAAAALqA2QAAAAAAgC5gNgAAAAAAoAuYDQAAAAAA6AJmAwAAAAAAuoDZAAAAAACALmA2AAAAAACgC5gNAAAAAADoAmYDAAAAAAC6gNkAAAAAAIAuYDYAAAAAAKALmA0AAAAAAOgCZgMAAAAAALqA2QAAAAAAgC5gNgAAAAAAoAuYDQAAAAAA6MDt9v8BONNavU0vLhcAAAAASUVORK5CYII=" alt=""/>


看看具体两者表结构的区别:

 select dbms_metadata.get_ddl('TABLE', 'T_LOB_SECURE') FROM DUAL;

 CREATE TABLE "SCOTT"." T_LOB_SECURE "
   (    "ID" NUMBER(*,0),
    "TXT" CLOB,
     PRIMARY KEY ("ID")
  USING INDEX PCTFREE 10 INITRANS 2 MAXTRANS 255
  STORAGE(INITIAL 1048576 NEXT 1048576 MINEXTENTS 1 MAXEXTENTS 2147483645
  PCTINCREA
SE 0 FREELISTS 1 FREELIST GROUPS 1
  BUFFER_POOL DEFAULT FLASH_CACHE DEFAULT CELL_FLASH_CACHE DEFAULT)
  TABLESPACE "TBS_TS1"  ENABLE
   ) SEGMENT CREATION IMMEDIATE
  PCTFREE 10 PCTUSED 40 INITRANS 1 MAXTRANS 255
 NOCOMPRESS LOGGING
  STORAGE(INITIAL 1048576 NEXT 1048576 MINEXTENTS 1 MAXEXTENTS 2147483645
  PCTINCREASE 0 FREELISTS 1 FREELIST GROUPS 1
  BUFFER_POOL DEFAULT FLASH_CACHE DEFAULT CELL_FLASH_CACHE DEFAULT)
  TABLESPACE "TBS_TS1"
 LOB ("TXT")
STORE AS SECUREFILE (
  TABLESPACE "TBS_TS1" ENABLE STORAGE IN ROW CHUNK 8192
  NOCACHE LOGGING  NOCOMPRESS  KEEP_DUPLICATES
  STORAGE(INITIAL 1048576 NEXT 1048576 MINEXTENTS 1 MAXEXTENTS 2147483645
  PCTINCREASE 0
  BUFFER_POOL DEFAULT FLASH_CACHE DEFAULT CELL_FLASH_CACHE DEFAULT))


 select dbms_metadata.get_ddl('TABLE', 'T_LOB') FROM DUAL;
  CREATE TABLE "SCOTT"."
T_LOB "
   (    "ID" NUMBER(*,0),
    "TXT" CLOB,
     PRIMARY KEY ("ID")
  USING INDEX PCTFREE 10 INITRANS 2 MAXTRANS 255
  STORAGE(INITIAL 1048576 NEXT 1048576 MINEXTENTS 1 MAXEXTENTS 2147483645
  PCTINCREASE 0 FREELISTS 1 FREELIST GROUPS 1
  BUFFER_POOL DEFAULT FLASH_CACHE DEFAULT CELL_FLASH_CACHE DEFAULT)
  TABLESPACE "TBS_TS1"  ENABLE
   ) SEGMENT CREATION IMMEDIATE
  PCTFREE 10 PCTUSED 40 INITRANS 1 MAXTRANS 255
 NOCOMPRESS LOGGING
  STORAGE(INITIAL 1048576 NEXT 1048576 MINEXTENTS 1 MAXEXTENTS 2147483645
  PCTINCREASE 0 FREELISTS 1 FREELIST GROUPS 1
  BUFFER_POOL DEFAULT FLASH_CACHE DEFAULT CELL_FLASH_CACHE DEFAULT)
  TABLESPACE "TBS_TS1"
 LOB ("TXT")
STORE AS BASICFILE (
  TABLESPACE "TBS_TS1"
ENABLE STORAGE IN ROW CHUNK 8192 RETENTION
  NOCACHE LOGGING
  STORAGE(INITIAL 1048576 NEXT 1048576 MINEXTENTS 1 MAXEXTENTS 2147483645
  PCTINCREASE 0 FREELISTS 1 FREELIST GROUPS 1
  BUFFER_POOL DEFAULT FLASH_CACHE DEFAULT CELL_FLASH_CACHE DEFAULT))

比较发现SECUREFILE  BASICFILE 大部分属性是一样。


  • LOB 如何存储数据

当创建 T_LOB_SECURE 表后,数据库会生成下面4个段。

SEGMENT_NAME                      SEGMENT_TYPE
T_LOB_SECURE                              TABLE
SYS_IL0000100726C00002$$        LOBINDEX
SYS_C0012385                               INDEX
SYS_LOB0000100726C00002$$    LOBSEGMENT

TABLE 是表,INDEX 是主键创建对应的索引约束.LOBINDEX 和LOBSEGMENT 是用来存储LOB 数据.实际上LOB 数据是存储在LOBSEGMENT中.LOBINDEX 是用于从LOB 中找出数据的某些片段.当创建lob列时,存储在行中的是一个指针,也叫lob定位器.当在读取数据的时候,就需要使用到这个lob 定位器.比如当要读取600到1200字节时,oracle会使用lob定位器和LOBINDEX 找出这些字节存储在哪里,然后再访问LOBSEGMENT.相当于先通过指针定位到地址,再读取数据.LOBINDEX 提高了整个效率.


  • LOB表空间

根据DDL 语句定义,不管用那种方式,store 后面的 tablespace 是存储 LOBSEGMENTLOBINDEX的表空间.

 LOB ("TXT") STORE AS BASICFILE (
  TABLESPACE "TBS_TS1"

 LOB ("TXT") STORE AS SECUREFILE (
  TABLESPACE "TBS_TS1"

LOB数据和表实际的所在的表空间可以不同:主要有两方面的考虑:

1.方便管理,数据和LOB 在不同的表空间,管理上互补干扰,还能提高备份恢复的效率。2.提高I/O性能,默认情绪下Oracle不会缓存LOB,所以每次读写操作都是物理I/O操作.表空间分开可以做存储IO能力针对性调整。

另外。 LOBINDEX和 LOBSEGMENT 必须在同一个表空间,无法分开。


  • ENABLE STORAGE IN ROW

管用 BASICFILE  还是 SECUREFILE  默认 都是 EN ABLE STORAGE IN ROW。这是控制LOB数据是否与表分开存储。如果是ENABLE,小于4000字节的LOB会像VARCHAR2一样寸在表本身中。这样只有大于4000字节时,才会存放到 LOBSEGMENT中。默认使用这种方式,不建议进行修改。enable能提高查询效率。


  • CHUNK 参数

LOB数据存储在chunk(片)中,LOB 索引会指向chunk,chunk是逻辑上连续的一组数据库块,是lob的最小分配单位。我们都知道数据库存储的最小分配单元是数据库块。chunk大小必须是oracle块大小的整数倍。chunk参数只适

用于 BASICFILE 。


  • RETENTION参数

LOB数据的读一致性和普通数据不一样。 LOBSEGMENT 并不适用UNDO段来记录其修改,而是直接使用 LOBSEGMENT 本身来维护多版本读。也就是说当修改一个LOB时,Oracle会分配一个新的chunk,修改的数据写入写的chunk,但是原来的chunk还会保留。也就是说 LOBSEGMENT的undo信息没有存在数据库的undo段中。


以上是LOB 的一些基础知识介绍。

下一篇介绍如何回收LOB 字段空间?



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